As has already been stated before, the brain is not fully formed until mid 20s.

So while technically 18 is the age of majority, that is just a technicality.

Depending upon the severity and nature of a crime, I think that younger than 18 can be considered "adult", and punishment should be made to fit the crime, as well as considering protecting society at large from vicious primitives.

It takes more to succeed than it used to. Things are more complicated than they used to be. Having a car at 18 wasn't normal until probably some time in the 1960s or 1970s. How much longer after that was it that car insurance became mandatory? Now people also need computers and smart phones. And antivirus and software and apps. And it just never stops. Frankly, I think adults should now have to bear responsibility for their kids past the age of 18, and it shouldn't be harder on them, either - extend the age for adult children being covered under family health insurance plans (although socialized medicine would take care of this, automatically).

Of course, the essence of human rights being increasingly as curtailed as it is, adulthood has actually been stripped from all of us.

If you are 20 and make content for tiktok, you are indeed a child.