I can still own my system just fine by choosing a phone with good community support and installing LineageOS (or some other variant of Android) + rooting it. If you don't want Gapps but still need to run apps which rely on it either microG or GrapheneOS with its sandbox are potential options. SafetyNet can also be bypassed if needed.

Now sure, that requires some extra effort and time from the user but it's just the situation we are in currently. Not like you have any other current options for an open mobile system outside of being an early adopter of GNU/Linux phones and their ecosystems.