What is the single worst thing about the API changes?

First of all, I post this as someone who is only modestly informed about the whole situation. I’m a casual user who moved here from Reddit mostly because of the blackout and I don’t have a super strong opinion about any of it.

I’m curious to learn though! Part of my curiosity is in the title - what’s the single worst thing the API changes have done (or will do)? Is it that they priced out Apollo? Is there another big third party app that’s getting killed?