The fediverse sounds just like what we all thought the internet was back in the early 90's.
Apart from Mozilla sabotaging the ideal in ways others describe here I can think of other ways it could be hijacked by corporate interests...
eg elimination of net neutrality so that ISP's prioritise traffic to paying servers, then doing deals with the biggest servers until we again only have a handful of options if we want wide reach?
Humans are suckers for hype and corporations know hype. While that is dangerous for democracy I have lost interest in communicating with the masses so being part of a relatively small network of people is just fine by me.