Did you just ignore all Super reboots?
Uub was created shortly after the defeat of Majin Buu, who until that moment was the most powerful that Goku had already faced. At the beginning of the Super, Goku faced Beerus, a God of Destruction thousands of times more powerful than Majin Buu.
Then Majin Buu became irrelevant.
It's not hard to imagine that they will not use Uub for something relevant. Just look at classic characters like Piccolo and Gohan, who are completely irrelevant now.
See how GT handled Uub. He is a character they will not know how to use, first because he was created to close the series, second because Goku will continue to be the protagonist, even if they reach to EoZ.