Sorry, but you no more get to make a definitive statement of what a fanbase is and isn't than I or anyone else does (and so you can keep your "spectacularly narrow" and "wrong" to yourself, thank you very much). You can of course have your own
understanding of what it is...
...and it would be helpful, given your arguments are based upon your own understanding, if you could say what it is. That way we could at least measure what you claim a fanbase can and cannot achieve (and can and cannot be responsible for) against that definition.
Oh, and if your understanding of the meanining of fanbase includes me as a member, it's far, far too broad.