I'll bite a bit.

I don't think Zenos ruined Endwalker. I think a lot of people really like him, and enjoyed seeing his conclusion (please god, let that be his conclusion). I'll admit, him showing up and having a couple of the best quotes in the expansion doesn't hurt as well:

"I assume this is your prey. But why does it still live? Surely it is no match for you"

"I would have thought you to be above something so banal as despair. Am I mistaken?"

Especially after 20 hours of "oh woe is us", having him just laugh it off was pretty funny.