The problem with "solving inequality" is there is no incentive for one to do better. If one can live as well as everyone else, with no effort, why should one make the effort?
Kind of a strawman though, innit? If "civilization will stagnate and humans will be unmotivated blobs" is one extreme, then the other is something like "condoning economic genocide".
In reality, few are concerned that Alice has a much nicer car than Bob, compared to concerns that Bob will die without insulin. Get Bob his insulin, and he will still be motivated to have a nicer car.
True, but I dont think any UBI scheme says "everyone live at the same level" more like "everyone gets enough to not die" which is a very different framing.
Work or die vs Work to gain additional benefits.