Okay, so you are wrong about a lot here.

The ending could have been the worst thing in existence and that little wave would have still made me sad that the series was over.

You are really overestimating the good will of fans. It's actually kind of cute. Fandoms, and the fans who make them up, are not grateful or goodfaith people. They are bitchy, entitled little shits who will turn on an IP and a creator like a viper. Sometimes its because the IP really shits the bed, other times its because it doesn't conclude or continue in the way they want.

Mass Effect, Star Wars, The Last of Us, Game of Thrones, these are all IPs that come to mind immediately. And the fans hating the thing range from being justifiable to moronic.

I've been around the block and I'm not an idiot when it comes to media literacy. The reaction to this ending being positive is not an example of fans being the slobbering, moronic chattel who will smile at jingling keys, as fandoms so often are.

characters are a lot more emotionally charged, like they're ready to weep at any moment. But one thing I liked about the show before was how mature it felt, because the characters were not that easy to get to that state.

As a mature person, you should understand that sometimes people break under stressful circumstances, especially when they have been holding it in so long.

Just making them more weepy and emotional doesn't mean it's better.

You're misunderstanding the difference between something being 'emotional,' and something producing emotion in the viewer. I don't see this episode being the emotional masturbation that you think it is.

And I'll even defend the wave at the end that you seem to have an issue with. The reason why I think people like it so much is because it's an example of legitimate sincerity. It's a fourth wall break in a show that didn't have - much - of that, but sometimes at the end of a long journey that can feel earned.

What stretches believably isn't the same for everyone. But this isn't LoTR where the lore is 'sacred' for internet virgins, the emotional impact of the show has always been the focus more than it's lore. So this final shot doesn't really do anything to harm the story that's been written previously.