No, the vast majority of Android phone owners are not going to open the command line. The very prospect of it will daunt them, or it may even be unfamiliar to them (a lot of Android users, especially in the developing world, rarely or never use a traditional computer and are unfamiliar with the full range of its features). Even those users who would copy and paste into the terminal are a niche more comparable to us here than the average phone owner.

Yes, of course sideloading may still remain possible in such a scenario, but it would not be mainstream enough to sustain any kind of mainstream ecosystem of apps outside of the Google Play Store. Even F-Droid supporters have been worried that clamping down on sideloading could marginalize F-Droid even further than it already is.