Would you like it to grow so all of your other, non-technical interests could have active communities? Do you want more people for moral and philosophical reasons? Or are you enjoying being in a niche? Are you happy to have a platform full of techie individuals, even in communities not explicitly tied to anything techie (much like this one)?
My answer to all of these is “yes,” so I’m not quite sure what I want. What are your thoughts?
I don’t run my own instance, but one concern I see grappled with by instances, at some time in their existence, is how to handle image storage and embedding. I won’t pretend to know the options or have opinions on which to use or how to resolve the larger issues, but I see that as a large hurdle to mainstream, in addition to the points referenced by OP.