What still throws me off is your mention of Zoro, Nami, and Ussop. I can understand being critical of certain aspects, and the MHA Anime has some serious pacing issue, but that comparison doesn't make any sense.
Deku is the main character
All 'Merica Might - is a super character. His continued appearance in the show as a motivating factor for Deku as well as his interactions with him don't have a direct comparison with One Piece or most other Shounen. Luffy looked up to Shanks, but for most of the series only appeared in sparse flashbacks. Naruto might spend a lot of time hanging out with Kakashi as his teacher, but he had no effect like All Might on why Naruto wanted to become a Ninja. Iruka kind of matches as a supportive force before he graduates, but still not the same level of influence as All Might
Bakugou is certainly not supposed to be likeable, unless you are DTL
Iida is supposed to appear as an unlikeable uptight guy that ends up being an alright classmate and friend to Deku. He has his own faults that is seen during the entrance exam.
Uraraka - A really nice cheerful girl. A person Deku needs for support and she will need him too.
Then you have the rest of the class that you don't know their quirks and personalities.
You also have a teacher in Home Teacher Aizawa, who you could think of as a Kakashi, a teacher that seems mean at first but actually cares for his students.
I think you are having a case of the time released blues whereas you probably started One Piece with a huge number of episodes or chapters available to speed through.
Let's go through the first six episodes of One Piece.
Episode 1
The series begins with an attack on a cruise ship at the hands of Alvida. Coby, a slave of Alvida, discovers a barrel. One of Alvida's pirates attempts to open the barrel, but a young boy emerges and accidentally hits him. The remaining pirates attack him, but the stranger stops them and says that his name is Monkey D. Luffy. Luffy drags Coby to the storage cellar of the ship, where he eats and converses with Coby, who reveals his dream of being a marine. Alvida confronts Luffy, but he escapes and knocks her pirate crew down with his Devil Fruit power. Luffy explains that he ate the Gum-Gum Fruit, therefore he has the powers of rubber. Coby, inspired by Luffy, stands up for himself when Alvida confronts them. Luffy uses his Gum-Gum Pistol technique on Alvida. Luffy and Coby sail away in a "borrowed" boat from Alvida's crew. Luffy asks about the pirate hunter Coby mentioned earlier. Coby says that he was captured by the Marines, and Luffy announces his intention of asking him to join his crew.
We are introduced to Luffy and Coby. Setting us up to meet Zoro in the next episode
Episode 2
Luffy and Coby arrive at an island with a large Marine base, where Luffy discovers the swordsman, Roronoa Zoro tied to a pole. Rika, a young girl, offers Zoro some rice balls that she made herself. Helmeppo, the son of Marine Captain Morgan, discovers this and has Rika thrown out. Luffy asks Zoro to join his crew, but Zoro refuses and has Luffy give him the rice balls. Luffy and Coby meet Rika in town, who is happy to hear that Zoro enjoyed the rice balls. She tells them how Helmeppo brought his vicious pet dog into their bar and that Zoro knocked it out to protect everyone inside. He then made a deal with Helmeppo: if he can survive being tied to a pole with no food or water for thirty days, then Helmeppo will spare the people in the bar. However, Helmeppo says that he will execute Zoro the next day despite his word. Luffy punches him, and Helmeppo runs off to tell his father. While Luffy invades the Navy base to find Zoro's swords, Coby attempts to untie Zoro and explains the situation to him. Morgan orders that they are both to be executed. The soldiers open fire, however, before the bullets can reach them, Luffy leaps from the base and uses his rubber body to block the bullets.
We are introduced to Zoro. He is shown to be a honorable person. Episode ends before conflict is resolved.
Episode 3
Luffy hands the three swords to Zoro in exchange for Zoro joining his crew. Luffy and Morgan engage in battle. All of Morgan's attacks miss and Luffy knocks Morgan to the ground. Meanwhile, Helmeppo takes Coby hostage. But Coby declares that he will not stand in the way of Luffy's dream, even if it means death. Luffy strikes Helmeppo, while Zoro takes out Morgan right before he can kill Luffy. As Morgan collapses, the Marines toss their weapons into the air in celebration of their captain's defeat. Later, Luffy, Zoro, and Coby are in the town restaurant with Rika and her mom. Marines step into the restaurant, and as Luffy and Zoro are pirates, they must leave the island immediately. Luffy and Zoro get ready to go, and the head of the Marines asks if Coby is with them. Luffy goes on to explain that Coby spent time aboard Alvida's pirate ship as her slave, and this makes Coby angry as it will ruin his chances of enrolling in the Marines. Coby punches Luffy. The Marines see Coby is not with them, and so order Luffy and Zoro to leave. As they do, Coby asks to join the Marines, and is accepted. Outside, Luffy and Zoro climb into their boat, and as they set sail, the Marines salute them for saving the town, including Coby. Coby vows to meet Luffy again, as a Marine meeting a pirate.
Zoro joins Luffy's crew. Coby leaves
Episode 4
In a flashback, a seven-year-old Luffy sits in a bar filled with the pirate crew of the "Red-Haired" Shanks, begging him to take him out to sea. But the pirate captain refuses. A bandit named Higuma enters and orders several barrels of booze. Shanks offers him the last bottle but Higuma smashes it and humiliates Shanks. After the bandit leaves the bar, all of the pirates start to laugh. Luffy gets angry that Shanks did not fight back and in a huff eats a purple fruit lying on the bar. Shanks notices this and tries to make Luffy spit it out, but it was too late. Shanks tells Luffy that he just ate the Gum Gum Fruit, a Devil Fruit, and now he is a rubber man and won't be able to ever swim again. Later, Luffy gets attacked by Higuma and his bandits. He is about to be killed, when Shanks and his crew arrive and effortlessly defeat Higuma's men. Frightened, Higuma throws down a smoke bomb and makes his escape, taking Luffy with him. He flees out to sea in a boat. There he throws the non-swimmer into the water. As Higuma laughs at Luffy's plight, a Sea King appears behind him and devours him whole. The sea monster then goes for Luffy, but Shanks stops the sea monster as it takes a bite, and with one look, drives the beast away. Luffy clutches Shanks and starts crying, since Shanks' arm was bitten off by the creature. Shanks replies that it is fine, as long as Luffy is safe. As the pirates get ready to leave, Luffy decides he will become a pirate on his own, that he will gather a crew that will beat Shanks', and that he will become King of the Pirates. Shanks gives his straw hat to Luffy and tells him to return it some day, as a great pirate. Back in the present, Luffy slingshots into the sky to catch a bird. Instead he is caught himself. Zoro, now alone in their boat, tries to keep up, paddling. On his way he picks up three castaways from Buggy's crew. The bird, carrying Luffy flies over a town, where it is shot down by Buggy's men. Luffy falls down and lands right in front of Nami, who is running away from Buggy's crew for stealing their precious map to the Grand Line.
Flashback episode. Shows Luffy's interactions with Shanks, how Luffy got his power, and the start of Luffy's dream to become King of the Pirates. At the very end Nami is introduced.
Episode 5
Nami pretends that Luffy is her boss, using the distraction to escape from Buggy's men. After Luffy beats them, she asks him to join her. Then Luffy finds out that she is a navigator, and asks her to join his crew of pirates. As she hates pirates, she refuses. Then she tricks Luffy into letting himself be tied up and brought to Buggy, where he is locked up in a small cage, while Nami fakes joining Buggy's crew. As proof of loyalty, Buggy demands of Nami to kill Luffy, but she cannot bring herself to do it. As Buggy's pirates attack her, Zoro arrives to save his captain and her. Buggy recognizes Zoro as the pirate hunter and attacks him. Zoro cuts Buggy into pieces. Believing Buggy to be dead, he sheaths his swords and is stabbed in the back. The wound puts Zoro at a disadvantage. He picks up the cage with Luffy inside and the three escape.
While Nami develops into a great character, at this point all we see is a character that doesn't seem trustworthy.
Episode 6
Still trapped in the cage, Luffy meets a small dog guarding his master's store, despite knowing that his owner is dead. Mohji the Beast Tamer's lion, Ritchie, inadvertently breaks Luffy's cage open, and sends him flying. The dog tries to protect the store, but is no match for the much stronger Ritchie, and Mohji burns the store down. Angered by Mohji destroying what the dog finds precious, Luffy mercilessly punches him out. Moved by Luffy's concern for the dog, Nami agrees to work with Luffy for the time being.
Those six episodes where not much exposition was done on the characters nor much happened in the plot, yet this is the same amount of time we have had exposure with My Hero Academia. In this time we have had Deku's motivations and hard work shown, All Might's influence on Deku as well as his continued mentoring of him and now the other students, a seemingly non-complex character (like Luffy), but an asshole in Bakugou, the seemingly female lead in Uraraka as a moral support for Deku, a friend in Iida, and a teacher that seems hard as nails but actually cares about his students in Aizawa. Then you have the rest of the class that has been minorly introduced at this point but will surely get more screentime and focus in the future.
Let me put it this way, Deku's mom has had as much focus on her as half of the one piece cast at this point.
