the problem here is that every single one of these alternate OSs requires advanced knowledge. Granted, it's not difficult to flash your phone via a USB cable + web interface but consider that the average smartphone user isn't even interested in removing bloatware like facebook.

The advanced knowledge i'm referring to is to first know that GrapheneOS exists, know how to enable OEM unlocking, know how to select the correct factory image and so on.

People don't care and cannot be expected to care. Apple, as much as i dislike several of their practices, provide a phone that works when you need it to. AFAIK, the iphone's primary purpose as a phone - has never had an incident where a software bug prevented someone from placing a call.

Graphene is still based on AOSP, right? I'm still hoping for something like postmarketOS where it does not use a android base.