I HIGHLY recommend sticking with it. It's kind of like Dragon's Dogma in that all the story is packed at the end.
The combat is fantastic once you get used to it. Took me a while to really pick up on some of the best ways to use class abilitiies because there are quite a few.
My advice is to just get used to using the available tools for sorting all the excess gear. 1) Quickly pick the best stuff for your slots that you want to equip following a mission. 2) Lock stuff you want to keep maybe for later (on the item menu, not equip menu). 3) Hit select all and dismantle all so you're not doing that over and over and over. You can sort gear in about 2-3 minutes this way. It's one of the only downsides is that this part is a little tedious. In the systems setting menu they also added a auto-dismantle option. Up the level minimum on that as you progress and it saves you time.
Things that are huge in this game that are not in Nioh as much, hitting enemies in the back is a critical hit every time. Huge damage bonus. Exploit elemental weaknesses, and change which combo finishers you're equipped with when certain enemies become common (you can combo finish with an element sometimes). Use your teammates if you're getting bodied, left / right on dpad on PS5. There's little tricks I've found for many of the classes that are extremely fun. My favorite classes so far are White Mage, Pugilist, and Knight, and they play completely differently. Also huge is that your break gauge refills slowly because they want you to switch classes frequently. When you hop to your 2nd class, you get a 2nd break gauge, so if you miss your counter or have to block a lot, switch to get a fresh fatigue bar.
If you're getting smashed on bosses, you have lots of options to rethink strategy: leveling, gearing up, changing combos equipped, changing classes, and bosses also have lots of hidden weaknesses or specific strategies that are effective. I've found that using my brain and trying to rethink strategy suddenly had me doing a lot better when I got stuck.