Well, let's say that I could hypothetically buy both the Google store and the Apple store, and I raised the percentage cut from 30% to 95% on all sales.

I'll even make it so that all apps are automatically available in both stores! And I'll use the revenue to buy out any competitors, or sue those who I can not buy.

would that still be fair? After all, I am providing a service, am I not?

I think the debate here is not about whether or not there is a service being provided -- but rather what kind of service fee would be "fair" in exchange for the service they provided, while acknowledging their (near) monopoly on android users.

In fact, people often do say that telecoms are monopolistic or oligopolistic, that they engage in anti-competitive behavior that is terrible for consumers, and that they should be broken up and/or strictly regulated. That has been a very prominent argument for many decades.