Earlier quoted context omitted.
And no sustainable way to fund it.
I don't get how people keep saying this. A UBI is effectively a tax credit. You fund it with higher nominal rates. These mostly cancel out for working people, netting to zero in the middle. People at the top pay on net so that people at the bottom receive on net. It's completely sustainable and is effectively just a simplification and improvement of the status quo of having unemployment insurance and a bunch of means…
b) Observe the real world, see what happens when you "just increase tax rate". You'll find that very often when you increase taxes you actually end up collecting less, as more people decide to illegally dodge taxes or simply close up shop.
Given a country's economic output, laws, culture and a thousand other factors, there's a hidden function that determines the maximum tax rate you can employ where anything more than that is counter-productive with both short-term and long-term results, the latter often including reputational damage that can be nigh impossible to repair, soft-capping your economy far below what it could've been. See: Laffer Curve, and the shining example that is Argentina.