Plus building it is kind of the easy part -- the hard part is getting people to migrate over and having enough active posts / users that people feel it's worth their time to stay and post as well. Migration will inevitably splinter communities as well, especially small ones, where not enough people move over (or don't move quickly enough). I've seen so many alternatives where the userbase was too small or not posting enough or just right wing trolls or the site was unusably buggy. lemmy managed to be good enough in all those categories at the perfect time - when reddit spat in the face of their users.