I may prove to be wrong but I'm looking forward to seeing how this plays out & genuinely think it could be good, holistically.
There's a number of possibilities:
1. This drives most people to Apple & Android dies. iOS is mostly a better product than Android, with the exception that Android is semi-open. This removes Android's only competitive advantage.
2. This drives most people to Apple which motivates Google to do a U-turn.
3. This drives people to Graphene in such large numbers that it gets financial support, & some banks are pressurised into dropping Play Protect requirements.
I honestly don't know which of these 3 is most or least likely but all move us away from the current stagnant position of Google being the best reasonable option of a set of very bad options. A complete Apple monopoly would obviously be bad in the short term but would at least leave an opening for fresh competitors.
But the % of the total market that do care is not an insignificant % of the total Android userbase. There's also a spectrum of concern - I'm a long time Android user turned iOS user: I care deeply about sideloading but ultimately the balance of pros & cons shifted for me, & I suspect will begin to for others.