We as a society would profit from not categorizing everything in terms of its usefulness. Things can and should be allowed to just be. That being said, UBI would probably result in more useful things not less. There are so many cases of jobs and things that seem to just be busywork or outright scams. There are also a lot of things that only appear useful if you never take the time to think about them. A plastic straw that will pollute the environment for thousands of years just so i can have a drink for two minutes? That is useless. Every street in every city being lined by cars that don't move for 95% of the time? That is useless and insane. Imagine what marvelous machines we could have built instead.

Also, I find the online discussion around UBI to be quite weird. I don't think anyone serious is advocating for it to be particularly high. In my opinion, UBI should cover your necessities plus some so you can participate in society. This gives everyone the opportunity to take it slow or focus on personal projects without fear. Everything luxurious can not, and should not, be affordable with UBI. This will leave ample opportunity for people to still care about and want to work.

Humans will always do. It is in our nature. But not letting people get homeless or starve to death might enable those of us that don't want to do what our overlords deem useful to do the things our society so desperately needs. I don't need some poor fool to cook my burger for me. I'd rather take turns with my friends that now have free time.

I hope you don't take this as a negative, but sometimes I wish I could think like people like you, very positive, but maybe I'm old/cynical?

There is a problem with "plus some so you can participate in society"

In a massive society this will never be agreed to. The 'some' here will never be enough. Too little and it's not UBI, too much and impossible to fund. Who is going to define what a luxury is? Is owning your own home a luxury, a car, washer and dryer?