Not sure I agree with both parts of your premise, there. Young drivers can pass their tests, and then on the first day that they have their license, go out in some Lamborghini supercar unsupervised on the motorway, finances allowing. It encourages a 'I have this bit of plastic, I'm as good as anyone' mentality; together with the general impetuosity of youth, you get the risky, accident-causing behaviour.

Compare that to a motorbike license - pass driving theory and CBT, and then a practical test, and you get the bog-standard licence to ride a chicken-chaser moped. You can then work your way up the licences, with minimum age requirements and time for holding each, until you have access to the big bikes, finances allowing. Make car drivers do the same, that'll cut down on the risky behaviour and the scale of the accidents that they could cause.

Admittedly, about the shittiest car that you can buy now will still do a hundred miles an hour, so you'd need some artificial limitations on power and which roads you can use..

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1056066/how-to-get-a-motorcycle-licence.pdf