As more people join the #Fediverse, some instances will likely need to pause new registrations while they allow their existing community to absorb new members. This is a *good* thing and no different from towns limiting new housing developments based on what town infrastructure can handle. The town/city governance metaphor applies pretty well to the Fediverse in my opinion.
In the physical world I've seen a large influx of folks moving to my town over the past few years and it definitely has had a number of negative impacts (along with some positive) as town infrastructure tries to keep up with the growth and change in culture. Metering growth based on the speed you can manage it makes sense.
