They created a good product so people used it and there were no alternatives when it got shit.

They created an inherently centralizing implementation of a video sharing platform. Even if it was done with good intentions (which it wasn't, it was some capitalist's hustle, and its social importance is a side effect), we should basically always condemn centralizing implementations of a given technology because they reinforce existing power structures regardless of the intentions of their creators.

It's their fault because they're a corporation that does what corporations do. Even when corporations try to do right by the world (which is an extremely generous appraisal of YouTube's existence), they still manage to create centralizing technologies that ultimately serve to reinforce their existing power, because that's all they can do. Otherwise, they would have set themselves up as a non-profit or some other type of organization. I refuse to accept the notion of a good corporation.

There’s no lock in. They don’t force you off the platform if you post elsewhere (like twitch did).

That's a good point, but while there isn't a de jure lock-in for creators, there is a de facto lock-in that prevents them from migrating elsewhere. Namely, that YouTube is a centralized, proprietary service, which can't be accessed from other services.