I agree, but it's not either/or. Some people will probably earn their basic income+extra doing science/engineering/etc, some will do art, and some will do the bare minimum.
If we successfully decouple work from sustenance, I'm pretty sure there will be a non-negligable percentage of humans who would just take the basic income and passively consume. However, letting a person consume without any "skin in the game," I think would create a sense of entitlement among the bottom tiers, and resentment among the productive segments of society.
Also, there will still probably be a bunch of stuff that needs to get done cheaply (i.e. 100% automation is not practical), but not enough people want to do, like picking up trash, or cutting the grass, or sorting files at a courthouse.
I just don't see a world where everyone does exactly what they want to do at all times forever, unless we build personal VR universes for everyone.
Also, I've spent a good deal of time thinking recently about how to quantify art and other "indirect" contributions to society under a basic income system. Like if there's any work requirement, even if it's minimal, how much art qualifies? A couple of doodles? Could I just randomly scribble some blotches on canvas and call it a week of work? Could there be enough qualified art judges to determine if everyone who will inevitably try to phone it in has contributed "enough?"
I don't know. This came out kind of rambly, but there's a lot of non-binary, non-obvious aspects to basic income, and I've struggled to find answers to a lot of the questions I've come up with.
Ultimately, I agree with you. The system should support people contributing in the way the enjoy the most.