Not remotely similar at all. Right now if you don't like Facebook, there's nothing you can do to change it... but hypothetically if Facebook ran its infrastruct

Not remotely similar at all. Right now if you don't like Facebook, there's nothing you can do to change it... but hypothetically if Facebook ran its infrastructure on a decentralized platform like Ethereum, then anyone could trivially fork the entire system with backwards integration. It's similar to how if someone doesn't like Chrome, they can fork Chromium and make their own version of it and keep complete compatibility with Chromium. The decentralized web does a similar thing except it does it for services instead of strictly software. It's a fully transparent and accessible ecosystem of services whose entire history is immutable and available for anyone to access. That said, no blockchain technology is remotely close to the point where a massive system like Facebook could possibly hope to run and it may never get to that point either, it's hard enough getting even trivial services to be cost effective on Ethereum... but in principle that's the idea.