Since the hot topic for a while is gonna be Attack on Titan's finale, I'll add my two cents.
I'll admit I haven't watched it for a while, I think the wait time between seasons was just ridiculous, it would take them upwards of two years to even catch up, which just tells me they weren't even working on it consistently, and the final season being split into parts just felt like a cheap way to keep up hype above all else. I respect that they waited instead of packing it with filler, but I still think they took much longer than they should've. I ended up spoiling the ending for myself because I got tired of waiting, and honestly, I can see why they'd consider it disappointing in a number of ways.
AOT always felt like a show to me that got too big for its britches, it kept adding new characters, new plot twists, new things to be resolved, and some of it wasn't up to scrutiny for me. When you make a complex series, the ending could be that much harder to make satisfying, but if you're the writer, you truly should know best. The final episode sits at a 8.6/10 stars on IMDb, which might be good for an average episode, but for the finale of an entire series, especially one with almost 100 episodes and 10 years of history, that's considered disappointing. These numbers might not seem like they make much of a difference, but they really do, especially at that point and from literally tens of thousands of reviews, meaning it's not gonna get any better. My gripe with it is that final stinger, it just feels really cheap to end on a cliffhanger like that after all the time they put into so many plot points, it feels like the final scene and moments kind of ruin it, and again, those are probably some of the most important parts of a final episode. It also feels like they didn't tie up a bunch of major plot points that they should've.
I'm not saying a series finale is bad if it's a cliffhanger, in fact there's some amazing series finales that are cliffhangers, like The Wire, The Shield, Homeland and The Expanse, but the difference between those and AOT's finale is that they had complex problems that couldn't ever be solved and their final episodes each reflected that but still offered closure to the storyline they were telling and the characters they were following. I know they're different entirely from AOT, but I also think that's irrelevant. I think what makes a good and bad series finale is completely independent of genre or style, it all comes down to competence. And it's natural to start getting burnt out if you're writing a complex story, but the ending is something that should always be at the forefront of your mind, especially as you get to there.
Ultimately, I'm not too surprised that the ending is being similarly divisive because the ending of the manga was largely considered disappointing, and sometimes the journey is more interesting than the destination, but the destination should at least be rewarding in its own right. I've seen stories that were much more complex and had much better endings. That being said, a disappointing ending won't inherently ruin an entire series, but it also kind of proves my earlier point, that it's a bit too big for its britches.
Sorry this post is so long, but keep in mind that I cut out a few things to shorten it. Feel free to debate respectfully, but I won't tolerate harassment for my opinion.
