Even? Tim Berners-Lee tried since day 0 to make the web decentralized. One of the initial requirements in the 1989 proposal for a global hypertext system included "Non-Centralisation" where "new system must allow existing systems to be linked together without requiring any central control or coordination". See https://www.w3.org/History/1989/proposal.html for the rest.

While it went OK-ish for the internet, we massively screwed it up for the web.

No we didn't. The web is very nicely decentralised, especially with the general malaise and decline of Facebook.

What isn't decentralised is web apps but TBL never intended the web to be used for full blown desktop app replacements in the first place so no surprise it doesn't meet its design goals for that.