- facebook used to maintain CSSTransition for animation but dropped support for it and gave it to a dude who broke not only the public API but also some features I was relying on. I'm left having to recreate all the animation in a different lib, meh

- lifecycles related deprecation: componentWillMount, componentWillReceiveProps, componentWillUpdate. My app used to have a lot of these but that's the easy part to migrate, the problem comes when third party libraries use those and nobody support those anymore

- method deprecation which brake third party libraries: findDOMNode. The 2 one I've used that relied on it: dnd and csstransition. There's no clear path forward that would take less than a few days to migrate my code, meh

- upgrading webpack to whatever your config should look like in 2021 and what new plugin for x is named

Nothing very specific to react in particular but for simple use case jquery or plain javascript tends to create less problems to maintain things over longer period of time

As far as the community is concerned, hooks has been a positive change when used correctly but it's not because you can do something using hooks that you should, some of those abstraction are over-engineeringly absurd (eg: https://react-native-aria.geekyants.com/docs/useCheckbox#exa..., https://react-table.tanstack.com/docs/api/useExpanded, ...)