Are they? There's Vimeo, Facebook, Pornhub's SFW option, Twitter can host short videos, there's a metric shitload of porn hosts, and if you're in for premium service every major CDN offers video hosting/distribution.
There’s no problem hosting wacky content. What people complain is they don’t get free hosting and advertising.
YouTube's dominance is not because video is impossible to host but because YouTube takes care of the advertising/revenue aspect for content creators. Any competitor would need to provide a similar service, and that's hard to do at the same level when you're not run by the world's largest advertising company. A serious alternative to YouTube would need to draw creators like YouTube does, and you need some sort of built-in way to (probably economically) incentivize them to create videos and put them on your platform.
I followed your link, then struggled to find something as you have to choose from a list of thumbnails. I then clicked to view something and immediately hit a paywall.
How are you supposed to "discover" this content? That is where youtube is so strong. Often on youtube I will be directed to patreon, etc - does this work on the same principle?
A lot of large YouTubers (like Wendover Productions/Half as Interesting) have been doing sponsored ads for a thing called 'CuriosityStream' which is basically Netflix for Documentaries/Non-Fiction and as part of a bundle if you subscribe with their link you get Nebula for free as an extra for as long as you pay for CS.
It's mainly existing content from YouTubers but with premium exclusive videos like Patreon has.
To be a little extreme: If we limited your freedom of speech by saying you can speak freely, but only in your own house, then that would still effectively curtail your rights. Whilst being technically true that you'd still have the right to speak, it wouldn't be in the spirit of freedom of speech.
This situation seems similar to me.
I think there's an argument to say, for the biggest providers of web communications, that if you would be allowed to stand on the street corner and say your bit that those providers shouldn't be allowed to prevent you speaking that 'bit' either.
Obviously as with IRL speech you have no right to an audience; none of us need listen. And, the provider has no curtailment of providing counter-points adjacent to your "speech", just as counter-protest is a normal part of protesting.
This ability to speak in ostensibly public forums is a natural and necessary part of democracy. IMO we should act to maintain that.
I'd add a couple of provisos:
# warnings on extreme content are fine
# the platform can demand those who are "speaking" be identified by name and nationality