Since you're asking for 'downvote comments': UI themeing had already been solved decades ago, there's absolutely no need to bring AI into play for a solution to a problem that doesn't exist in the first place - on the other hand I get the impression that this is the one thing that AI is really good at ;)
But back to the topic: The reason why UIs are no longer themeable has zero technical reason, instead it's a cultural problem (the introduction of artificial 'fashion cycles' into UI design for no other reason than justifying the existence of a 'UI designer' job role.
There is clearly a need: adding AI gets your company funding, looks great on your CV and lets you brag to the board that your AI strategy is moving along
But back to the topic: The reason why UIs are no longer themeable has zero technical reason, instead it's a cultural problem (the introduction of artificial 'fashion cycles' into UI design for no other reason than justifying the existence of a 'UI designer' job role.