Fediverse is really still in its infancy. Its only just shifted from those with a lot of technical knowledge to those with a fluency of it.
It's when the average person can create an account and start engaging that it will reach critical mass.
It's not a bad thing that its taking a while to get there so that certain cultures, terms of engagement and stable/viable instances (each with their funding streams) can be established. If there were a sudden mass exodus from centralised systems to the fediverse, it would just mean a massive loss of the signal to noise ratio rather than a slow, measure integration of each wave of new users.