In fairness, when have they ever really tried? Disneyland 1955 was really the only time a Tomorrowland attempted to genuinely predict anything, and even then it was still mostly reliant on demonstrations of cutting-edge technologies more than attractions based in an ever-expiring future. Since that version the Tomorrowlands have always been at good bit “out there”.
People like to talk about how “the Future always catches up to you” but forget that it’s never really caught up to Space Mountain. The trick is to do roughly what you said - create a vision of a Tomorrow that always was and never will be - only they need to really renew their commitment and double down on that with an attraction lineup that is fun, exciting, and unified around the actual theme. When they’ve done that it has actually worked. And more than once! But over time they dilute it and screw it up, and THAT is the issue.
The problem isn’t that Tomorrowland can’t work, it’s that they aren’t even trying to let it work.