Uber & Airbnb were really exploring a time-honoured model that has predictable effects. Taking underutilized resources and shifting to a "rental" model increases utilization of assets, broadening accessibility, and thereby increasing wealth... while simultaneously increasing the value of the underlying asset (making it less affordable). This isn't a new thing, or a surprising thing, nor is the scale of it the problem.
Where we get into a problem is when, due to lack of competition, you start extracting almost all (or perhaps even somewhat more than all) of the value that you're adding. That leaves everyone else in the same boat they were in before the rental model showed up, except comparatively worse off because there's a ton of wealth in there that has been concentrated in the hands of a few.
This is the kind of thing that having more competition would help with.