as i see it they started off with some interesting concepts and research, then got pressured by VCs to deliver, into becoming just another twitter website clone with a sprinkle of federation theater 

 100%. 

VCs just create artificial growth. most don't make it past Series D 

 they do, this whole "scale or die" ideology, plus that they always (by definition) need to capture profit from the entire ecosystem somehow which is an inherently centralizing influence