It certainly doesn't help that Lemmy had and still has absolutely no sensible way to actually surface niche communities to its subscribers. Unlike Reddit, it doesn't weigh posts by their relative popularity within the community but only by total popularity/popularity within the instance. There's also zero form of community grouping (like Reddit's multireddits) - all of which effectively eliminates all niche communities from any sensible main view mode and floods those with shitty memes and even shittier politics only. This pretty much suffocated the initially enthusiastic niche tech communities I had subscribed to. They stood no chance to thrive and their untimely death was inevitable.

There are some very tepid attempts to remedy this in upcoming Lemmy builds, but I fear it's too little too late.

I fear that Lemmy was simply nowhere near mature enough when it mattered and it has been slowly bleeding users and content ever since. I sincerely hope I'm wrong, though.