I agree with everything you said, but especially these points. A while back there was the short-lived OMG My Game but I think it came at a bad time. But yeah, ultimately EoFF has always just been a hangout for nice and interesting people with low tolerance for jerks. The main problem is that people's tech preferences have changed. I think if you can't give people a good mobile experience, you're alienating a lot of potential new users.
Part of my Mastodon suggestion is because it addresses a lot of the technology and community-focus issues, and also has an "early adopter" bonus right now. EoFF got its early momentum as a Final Fantasy EZBoard in '99, before they became a dime a dozen. I think to keep that up you have to stay up with where your potential audience is moving. I think moving to Discord was a really good move in that sense, though obviously not everyone wants to hang out in chat rooms necessarily.
If we do a re-brand, we'd definitely have to keep the same forum database rather than set up shop elsewhere. I think many people come here out of habit, judging from the success (or lack thereof) of spin off forums over the years. Break the habit and it's goodbye Piccadilly, farewell Leicester Square.
I wouldn't nix the forums ever, really, as long as vBulletin stays around. But I think you could probably re-organize with a lower emphasis on FF and engagement wouldn't deteriorate so bad (ie hiding the FF stuff as subforums or something)