Basic income has many of the same upsides, but the downsides are mostly about the dollar cost.
It's not unreasonable that some people prefer to pay (eg) higher taxes than suffer various forms of corruption.
I will take UBI or negative income tax every day of the week over unions.
In fact, if they were championed by - shall we call them economic liberals? - then they might be a damned sight harder to subvert and be a whole lot more effective and palatable. I know Sweden has strong unions and workers on boards (something I learnt from the very readable though still arguable book 23 Things They Don't Tell You About Capitalism[1]), with restricted power (the employees can never become a majority in any vote on the board) and it seems to me to be an obviously good idea.
[1] https://en.wikipedia.org/wiki/23_Things_They_Don%27t_Tell_Yo...