Are you saying that you don't think startups seek to displace middle men and create monopolies? or are you saying companies with monopolies don't exploit those to overcharge people as much as possible?
Because neither of those statements is exactly controversial.
What I think, and what you think, is irrelevant. Back up your claims, or they're just you trying to convince yourself you know something you don't.
Cutting out the middle man does not by definition lead to monopolies, especially not when the market has tens of thousands of sellers (if not orders of magnitude more), and tens of thousands of buyers (or, renters, in this case. And again, if not orders of magnitudes more).
It’s not cutting out the middle man - it’s replacing the middle man with a software middle man. The only way that doesn’t lead to a monopoly is if there are multiple software middle men competing. Like, do you actually believe that uber is just a platform connecting buyers (riders) with sellers (drivers)? It’s a taxi company. It replaced a dozen taxi companies in each city with a monopoly or an duopoly (when lyft is also present).
Because neither of those statements is exactly controversial.