I am sure other platforms / personal hosting will continue to exist in the future. They simply won’t be relevant in terms of video streaming market share.
The network effect of youtube is massive. They have a huge amount of content creators and audience. That means the audience will stick around for the creators and the creators go for the biggest audience and hence the most views.
Being google, they have data centers all over the globe, provide a fast app / browser access for any OS, can cast to a TV with one click - all these equal convenience which cannot easily be beat by any individual website.
Some huge youtube brands like linus media group are trying with floatplane as their own paid video hosting service, but I’m sure their view numbers are insignificant compared to youtube even though they are the biggest players.