You don't have to.

This is the most secure option:

https://grapheneos.org/

This is more flexible and will give you root, at the cost of an unlocked bootloader:

https://lineageos.org/

You shouldn't, I agree with you, but what's the solution that works for everyone, not just the tech literate?

There doesn't need to be a solution that works for everyone. It doesn't matter how many barriers you put in place, people will always get scammed - so don't punish the other capable 85%.

You mean the capable 15%, not 85% as again users are dumb. That's why governments will always cater to the majority.

You do in fact need a system that works for the vast majority. If your system flat out doesnt work for 15% of the population, you'd have mass riots and unrest.