That creates a community. Getting people to actually use it is a different and much more complicated thing.
AFAIK there is work underway to make more Lemmy communities more like Matrix rooms, by allowing the mods of 2 or more communities on different servers to federate them, so every post or comment to one of them goes to all of them. But this too is political and complicated.
If it's not obvious why cooperation between the mods of different communities is political, I'm not sure how to explain it ; ) To be clear, I mean little-p political, not big-P Political (involving electoral politics and the accompanying partisanship).