I agree. There isn't even a need to create alternative OSes: they exist. Be it Linux phones or (more realistically for the vast majority of users) AOSP-based OSes like GrapheneOS and LineageOS.

The real problem is that:

1. Most manufacturers prevent us from unlocking the bootloader, adding custom signing keys and relocking it. Interestingly the Google Pixels allow that. This should be mandatory.

2. Many apps choose to ban alternative OSes by use of Play Integrity, i.e. checking that the OS is signed by Google. This should be illegal.

3. Bonus: it should be mandatory for manufacturers to make it reasonably easy to support from an alternative OS. That means publishing device trees, for instance. This should be mandatory.

I really believe we should fight for that. Then we wouldn't have to care about what Google does on their side.