Also there's the fact that companies can end up sharing data to other parties, or a company can be acquired and change their mind about what the data will be used for (which is allowed because of the originally nebulous scope of their T&C which was specifically designed to allow for expansion without asking for user consent explicitly when usage changes). GDPR provides methods for users to be protected in both of those cases -- while just enforcing education does not.
Not to mention that if education was mandatory, then the same companies complaining about GDPR today would be complaining about educating users how their services abuse their dignity. Cutting Google/Amazon/Facebook/etc slack for making hundreds of billions from users' personal data and creating "Big Brother"-esque profiling systems for their billions of users doesn't really seem rational to me.
If I owned a site I would not have a problem to delete someone's personal data.
Also your sugguestion is that if you want to keep your data protected then you should not be using anything on the Internet or make any deals because once you have ordered something on Amazon it can sell your data to everyone else? Or when you rent an apartment, realty agency should be allowed to share your name, SSN, bank card number and address with everyone? No, I don't think it should be this way.