The alternatives do exist and the 0.1% of people that want to use them, are. If more people want to use the fediverse in future thats great, but I don't want to just get people lumped under a particular umbrella because it's what I personally want. The fediverse doesn't need to be the biggest social media platform for me to feel validated.
The fediverse is a tool. I don't choose what tool to use based on what everyone's favourite tool is. I base it on the job at hand