YouTube is basically the only video platform where the vast majority video creators are gathered on. PeerTube and the likes are nice, but for the most part, don’t even play in the same league, IMHO. YMMV depending on the content you like to consume, of course.
I mostly use a combination of DDG/Brave, but I have to fall back on Google Search way more often than I’d like to find some things. Especially for local (geographically speaking) stuff or non-English content…
It sucks that they dominate so much, but it’s not particularly difficult to guess why your average person still use them, no?