To be fair, I think Lemmy has some usability issues that are probably holding it back some. Like, typing !CoolCommunity@some.other.instance will make a completely useless link to the other instance that doesn't let you subscribe to it or post there. There are also only two apps, and they're cool, but clearly unfinished. That's just a couple examples off the top of my head.

I think they're minor issues that will be ironed out relatively quickly, and whining about federation being unfathomable nerd stuff is just silly, but it is true that this is all happening before Lemmy was really ready for it, and a lot of casual users will be scared off by that.