There are a few options and none of them are great.
First we have to split between paying for content and paying for the delivery.
There is already a platform where people pay for the delivery by letting their device be part of the delivery system. That's Bittorrent. You can download by uploading. I don't see why something like the Bittorrent protocol couldn't be adapted to a Youtube like platform. And if the platform only serves a frotend that helps you find the correct torrent and then streams the content in a video player, the demands on the server would be low enough that it could be run using ddonations or something like that. It would basically be a legal version of the Pirate Bay.
For content creation on the other side, that's a whole different can of worms. Content creation takes much more money. I see only two alternatives to ads, sponsorships and direct payments: government-sponsored content and unpaid content.
Government-sponsored content like e.g. BBC stuff is good, but it doessn"t nearly fill every niche that Youtubers etc. currently cover.
Unpaid content could work for some media, e.g. there are a lot of great books or music made by hobbyists without commercial aspirations, but making high-production-value videos without propper funding is just not going to happen at scale.
So all in all, I don't see a future where we aren't going to pay for content in any way.