From my own experience with Lemmy, I can absolutely see why it's declining.
Lemmy is packed full of miserable people constantly calling for violence. 90% of the feed is packed full of US politics, it doesn't matter how many filters I use I still see that greasy orange cunt's face every time I open Lemmy.
The amount of hostility towards outsiders just getting into Lemmy is astounding, and I've absolutely seen the whole "quality over quantity" crap that only drives people away from the platform. The IT tech snobbery is also incredibly offputting to people who aren't tech enthusiests.
In short, Lemmy has a toxic shithead problem that a platform this small can't afford if it wants to survive long term.
It's always fun when there's a GUI tool for something (in my case, trying to set up wireguard with gnome) that just doesn't work, and all the posts online about it just say "yeah that's literally never worked, here's the cli command"
Or colour profiles for your monitor in Wayland, you can change them in the gui but nothing will ever apply.
I find myself having trust issues with Linux GUI tools as actually functioning seems to be optional. But the switches sure look pretty...