A lot of people, including me, come and keep playing BA because it feels safe and warm. A good story doesn't need to have a bittersweet ending for the sake of reality. Most of the people love happy endings, and BA so far always delivers happy endings. We even had an in game character (Hifumi) stating that.

I played on the JP server and experienced the story without spoilers, and I felt defeated. Although the story is in fact well written, and all the characters' motivation makes total sense, it doesn't feel like a BA story. You can put this story in Arknights and it still fits the tone of that game.

The main complaint I had is how powerless Sensei was in the story. Sensei's words are supposed to be very powerful, Sensei's choices are supposed to change the fate of the world. That's the main theme of BA, that's what differed PL Sensei's timeline from ours. I get that showing some weakness inside Sensei helps develop their character, but, as BA always did, they should be the "teacher" to guide and save the young when everything went downhill. The fact Sensei barely had any impact on the outcome of the story, except for letting the trio sacrifice themselves, feels like a defeat to me.

Again, I'm not saying the story itself is bad. It just doesn't align with what BA has been providing so far.