I don't understand the comparison. The Lemmy implementation of ActivityPub facilitates the creation of lots of instances, or servers. Lemmy isn't just the service, it's also a front-end. Why would we compare all of the Lemmy front-end instances with one instance of Kbin? Kbin is built on top of the Lemmy service. They all share the same scaffolding. This means we can be thankful that one instance of Lemmy, such as Lemmy.ml, is not gaining momentum, while being thankful that another instance, like Kbin.social, is.