The monopoly/gatekeeping effect of an OS developer making apps that compete with independent apps has such an easy solution. The OS must not give private api's

The monopoly/gatekeeping effect of an OS developer making apps that compete with independent apps has such an easy solution. The OS must not give private api's or special permissions to its in-house apps. Don't try to fight the gatekeeping feature by feature, that is whack-a-mole. Bonus points if you require the primary UI (window manager in the language of the ancients) to be an installable app.