The majority of people who contributed early cultural or scientific breakthroughs to western society came from privileged backgrounds where they had no need to work. This was overwhelmingly the case from ancient Greece through to the 19th century.
I don't think advocating for universal basic income is the same as expecting a utopia, thats just making a straw man assumptions about the motivations behind such an idea. Also 'this won't result in a utopia' is not a rational argument against universal basic income.
There's a notion in the western world that making people's lives easier in anyway will compromise their character or destroy society. This is an extremely unexamined assumption that most people make without realising and originates from the the barbaric and extreme forms of christianity that dominate our early history, it's our cultural interpretation of how original sin operates in society. Give women the vote and they will turn into beligerent man beating barren she-beasts, free the slaves and they will drink themselves to death because they have no supervision, banish capital punishment and everyone will murder whoever they lay eyes on because there is no strong deterrent not to, raise minimun wages and society will fall, teach the unwashed masses to read and society will fall. Time and time again it is the negative and uncharitable projection of what happens after society lifts it's standards that has proven to be naive. History is unquestionably in favor of universal basic income. I do think your concerns about inflation are valid but as with any other major social reform, people will figure out how to make the fundamental changes necessary to preserve their new expectations and values intact. It will probably just be rocky for a generation or two and then take a viable form.