Twitch has one of the worst developer experience I've seen. I developed a set of tools ~6 years ago and they get broken by API changes twice a year. Meanwhile my similar set of Steam tools have been running smoothly for a decade. They just love changing their APIs left and right, often without fully supporting all the previous functionality. They arbitrarily many functions harder on the developer for no reason (like how you now have to manually convert username into userid).

Also, since they switched their own internal API to GraphQL, they basically stopped caring about the developer API. That's the #1 thing, if a website doesn't use the same API that it provides developers, then chances are the API will be shit.