Surely the ability to pay for things exists already in many forms/platforms.
But one thing that's missing is central financing from the platform itself. The "big tech" is running wild with advertising money and this is what fuels the rapid growth.
Things like Nebula seem to work (creator owned business that offers paid subscriptions), but I'm not sure how many Nebula-exclusive creators there are, I have a feeling most of them publish stuff on YouTube as well.
Mastodon and Lemmy communities work on donations, but most of them just trundle along barely covering hosting costs.
I guess, in theory, it would be possible to create a PeerTube/Loops server that monetizes everything with ads, but I'm a bit skeptical of that unless you have very deep start-up VC money behind you to get you off the ground.
We've had micropayment/-donation sites like Flattr, but it never took off for real.
I think the core problem is trying to make people to pay for the content/service/membership. Most don't. I don't think that would change even if the option was integrated into platforms.