Honestly, the complaining is the standard "our clubhouse" kinda vibe you get absolutely every time this happens, where a community grows rapidly from small to medium. Literally, every single time.
While I understand the complaints, its always struck me as a little silly for people to make them in a place that was clearly intended to grow large. Like reddit for instance. Or a server called lemmy.world, seems to me to be signaling a clear intention to seek to become large.
I mean, yes, the tone changes. It's going to go through several evolutions, not just one. And every one of them will bring complaints. It's just people being people, "get off my lawn" is probably a sentiment roughly as old as the animal kingdom of biology?
That said, I deeply appreciate that the Fediverse actually has a built-in solution for them. Which they of course already know, they're just bitching and moaning, that's all.
Regarding community duplication, that is the system working as intended. If someone wants to combine them into one, it would not be difficult to make a program to do this.