It's a different unrelated group claiming that it shouldn't exist if it doesn't provide the pay / benefits they think it should.
See heavy drugs, prostitution and violence market as some examples where two consenting adults is not enough to form a legitimate business.
True: it is not the case that we should fundamentally allow any association between two consenting adults. No, this does not justify preventing it in other cases.
The way I see it, it's already proven that riders will accept paying X dollars and drivers will work for X dollars, minus Y% for Uber's cut. Uber's Y% is likely higher than it needs to be, but at the end of the day, it's a SaaS app. Even municipalities have set up local competitors / clones.
These companies are certainly pouring a ton of money into expanding into new geographic areas, other business models, and more. But as long as riders will pay an amount even a little higher than what drivers will accept, it can be profitable.
And there are plenty that argue that under capitalism one isn't fully free. There is always the threat of losing the roof over your head.
Then you can start thinking about real solutions to urban transit that have existed for more than a century.