The journey was more important. Shitty ending is shitty ending, but it doesn't take away from the greatness that came before it.
1. Choices throughout the trilogy only amount to a war score point system.
2. The entire intro is written for new players, which is why Shepard acts completely out of character that first hour. He'd rather stay on Earth and go pew pew, rather than uniting the galaxy.
3. Kai Leng is a cringy edgelord.
4. ME2 characters are completely pushed to the side.
5. Game keeps forcing you to feel sad about some random kid on Earth, writing your Shepard for you, even though the player had no personal attachment to the kid.
6. The final level of the Mass Effect Trilogy, the grand epic last battle that we've been building toward since we first saw Sovereign on Eden Prime in Mass Effect 1, amounted to shooting a bunch of husks on few streets of London.
7. The Crucible was a big smelly asspull of a Reaper Off Switch by the writers, because they wasted ME2 not setting up a proper way to fight the Reapers.
8. Dialogue choices are dumbed down.
9. Jessica Chobot.
10. The was obviously poor communication between the writers, because on one hand the game constantly hammers home to you that the Reapers can't be fought conventionally, and on the other hand there's Codex Entries of the current war, chronicling how some species are effectively fighting and destroying Reapers, conventionally.
But sure, the game was greatness before the ending.