True, and that's why you can only marginally change anything on the market with that. If no player on the market offers what you want, your only choices are to punish everyone (which they won't notice) or reward one of the least-bad players.
Both can set the wrong incentives for companies to change or continue.
Doesn't fit "small". It was also just an example, my actual requirements are longer. I need my banking apps to work too, for example, which likely automatically limits me to Android/iOS. No idea how good they work with Sailfish for example.
Might be worth a shot, but typically they even refuse to work on rooted androids, so I assume whatever security mechanism they expect, it won't be there.