I believe that the top-level comment you replied to is making the point that there should not be any authority that either allows or disallows what a user can do with the device they own. Purchasing a device should make one that authority, free to decide how much security to trade for how much privilege.

But really it's all about framing. For example on desktop computers it's not possible for people to create new instructions for their CPU to handle. At some layer there will be an API that user needs to use to interact with the device. As times goes on I think it's natural for that layer that users are expected to interact with their device with to become higher level. I believe the top level comment is framing this issue such that current phones don't have an API that matched how it worked for UNIX computers and that is a bad thing. The commenter is too focused on how things worked in the past and doesn't want to allow for things to change.

Okay, and how am I going to give the user the right to wipe all software from the device and use a completely custom software?

I mean, we all agree that such permissions are not required during everyday operations, but there should be a way for the consumer to have control over the software being used. And I mean all aspects of the software: firmware should be updatable, the OS should be replaceable, and the security concepts within the OS should be customizable by the user as well. I have no problem with hiding such functionality and requiring users to read the documentation to find out how it can be done, but it should still be possible.

Sure, but such a product requirement can be made to be legally required without legally requiring root access.