This was frankly just baffling, and unless you're into fanservice and don't really care about characters and a coherent plot, just skip this one even if you like the series.
For context, I've been enjoying the anime and the manga in the last few months or so, and I was looking forward to watch this. The art/animation in the anime is just beautiful and in this sense the film did not disappoint. The action scenes were all great as well.
The problem is that the tone was somewhat off compared to the previous 2 seasons and the manga. It's in fact an anime original (not based on the manga or a LN) and it shows, because it's a lot of fan pandering, mostly to the fujo, I guess. The manga barely has any of that, the anime did but in a sort of lighthearted Gintama way so it never felt bothersome before. Yaoi pandering to me is like ecchi; if I can avoid it I gladly do, as I find it generally lowers the tone.
The characterisation of many of the characters was also weird, as in characters regressing out of nowhere and making decisions that felt ooc, especially MC. The plot didn't make much sense, I kept thinking I missed bits and that's why I didn't get it, but turns out they were just plot-holes.
I hope this isn't a reflection of what a season 3 will look like, although given that they'll (I guess, right?) adapt from the manga again that shouldn't really be the case.