It was so easy that people strived very, very hard to make it seem complicated - and they succeeded. Back in the day every React tutorial layered in soooooo much other stuff, Redux and a million middleware layers that completely obscured what React was.
The core of React though is really simple and no amount of attempts at complexification can destroy that.
Hooks is really one of those things where you need an IDE to tell you that you’re doing it wrong, since there’s a whole bunch of footguns. It’s doing its best to solve a hard problem inside the limitations of JavaScript, but it is essentially a kludge.
Just like in Flex the difficulty (and don't get en wrong often extreme awful difficulty) comes when someone fights against the system and can cause a cascade of terribleness. There were always telltale red flags when looking at Flex code when someone tried to circumvent the component lifecycle and the same smell can be spotted in React code.