Part of it is a normal process: as a service becomes more popular, the group that started it loses influence. That began even earlier: Mastodon was started by Gargron, but he now has less control over how it evolves.
In principle, Mastodon’s growing popularity is good for everyone, because it will generally improve more…
“Single inheritance taxonomies are an anti-pattern.”
“It could be composition all the way down”
I would never argue that ES6 classes are “clearly a better choice than composition, modules, or prototypal OO”. They are not. I’m a fan of purely prototypal inheritance (I’ve even written a library for it), I’d love it if the semantics of classes were based on it. But that didn’t happen, for the legitimate reason of backward compatibility.