Yeah, but we used to call it the information superhighway and the worldwide web. Internet IS the good term. It may well be that fediverse sticks around so long that we all get used to it, but at the moment, eh. I think if someone somewhere suggests a good alternative, we'll all likely jump on it.
While you're correct, it's just a clunky term. I think some other way to refer to the whole thing will probably come along soon, and in a few years, people will regard saying fediverse the same way we look back on people talking about "surfing the information superhighway" or whatever.