I think for me it has been this way for a year or so. Maybe it is because I am on a VPN. I also cannot view YouTube videos on YouTube any longer, because it always wants me to log in, to "prove I am not a bot". So I have switched to only using invidious instances, and if they don't work, then I just cannot watch the video.

I wish content creators would think of their own good more, and start publishing on multiple platforms. Are there any terms that YouTube has for them, that reduce revenue, if they publish elsewhere as well? Or is it mostly just them being unaware?

It's a VPN thing, or a 'you've been downloading too much and are ratelimiting you' thing.