"All these services are easy to replace" - I would like to agree, but I think that statement trivializes the endeavor a bit too much.
For Docs for example: Sure, from a technical standpoint, creating a webapp that lets you modify a document, syncs over new changes on a regular basis, and lets multiple users collaborate on the same doc and the same time is certainly harder than making a hello world calculator, but it's definitely not that hard. Most of us could figure out how to do it, especially since it's 2021 and our hardware is up to the task.
However, what is stupidly non-easy, is getting billions of people to use your solution, and for it to become the "standard" in society, for powerusers and non-powerusers alike, and for it not to have hiccups when a billion people use it. Oh, also, you need to somehow pay for the physical infrastructure that supports it, and the human beings that maintain it (hardware + software).
The situation would be even more complicated for YouTube because of the nature of the content, i.e. a single video on YouTube might be viewed by billions of people, while even the most popular docs are viewed by thousands at most, and even then making a copy of a text document to then distribute off-platform is pretty trivial.
And yes, we can spit out terms like blockchain w/ proof of stake, IPFS, etc. - but the tech isn't even the hard part, it's everything else that's hard (adoption, consensus, complexity for non-powerusers, funding, etc.)