I don’t disagree, I do think there are too many communities for the number of active users (both here, and Lemmy in general). What I’d be interested to know is this: Is there some research into the subject, or even a write-up from someone who has successfully grown a thriving community in the past?

I’d argue that with !programming@programming.dev being the “default” community, this is somewhat mitigated. It’s not policed, so you can post there about Rust, Godot, Python, or whatever you like and nobody will moderate you or ask you to move along. Maybe the “over-dilution”, as you call it, hurts the instance as a whole. But if you think of Lemmy as something wider than a single instance, it matters less. !programming@programming.dev is the flagship instance here, and it’s a large one by Lemmy standards. People will subscribe to that from all over the Fediverse.

So I think it comes down to your view of programming.dev as an instance vs Lemmy as a network of federated communities. Ultimately, people will just subscribe to whatever instances interest them - and hopefully Lemmy as a whole will thrive, including this instance.