lemmy looks like it does now because it's first of all and most importantly small.

the reason why it's small is that there are barriers for entry, be it effort needed to understand federation for the first time or choosing instance. "ooh just choose anything it's not that hard" shut the fuck up. it's a barrier because you can see that numbers are quite low, and just because you've come through it already doesn't mean it's not there

but there's bigger issue. depending on instance and how do you count, some 95%+ of new active users could have been rexxiters. this means that by coming there they have to leave reddit, and that means leaving communities that were there

average person isn't stupid or malicious or unenlightened plebeian. average person is just. average. because of small lemmy's size people there are subject to strong selection bias, namely on gaussian distribution of "how much do you care about moving there" that's far right tail that sits there. what are reasons for that, for every person that would be a bit different. some of these are FOSS enthusiasts or techlibertarians or softcore anticapitalists. this has some serious implications. some were banned from reddit but want replacement (some of these were shown door already, like exploding-heads).

now, crossection of "people who cared to come there" and "programmers" is reasonably big, as evidenced by programming.dev, but for any other unrelated topic there's much less. crossection of "people who care" and "people who are good at identifying mushrooms" or "aviation fans" or whatever is small, maybe too small to form new community. these people would need to leave reddit and their community and come there, doing nothing because they have no other fellow mushroom identificators to talk to. so, many don't. there's also probably negative selection of specific kind of people like some conspiracy theorists, at least for now

if you want to see lemmy grow, you would see dilution of that concentrated techbro sentiment with people who are otherwise average, but these people are also there to form new, specialized communities. you might want to gatekeep them out with some eternal september scenario, but it most likely won't work. personally i think that lemmy needs to grow a few times over for these "unrelated communities" to form, and then things will get pretty sustainable

another thing is that there's no ads and no selection for hostile content or conspiracy theories, and that might be related to how lemmy's algorithm is not driven by engagement, at least that's how it looks like