The accident statistics (I can help find them if you want) are that accident risk goes down steadily until (IIRC) mid 60s, and only increases above the risk of 20-30 year olds at a very advanced age in your 80s.

There are two things going on:

1. Young people, especially young men are on average significantly more reckless than older people. This is a direct way in which age "grants you better driving capability" - you just become less of an idiot.
2. Young people on average have less driving experience than older people. That's not a direct result of age but it does correlate.

These are different processes but they can both be targeted for safety measures.

I've never seen a middle-lane hogger responsible for anything dangerous either - I'd put them firmly in the "annoying" category. Once in a while you see someone responding dangerously to someone driving in an annoying but otherwise basically safe way, and I also see this when the "annoying" way people are driving is driving at the speed limit, or waiting for a safe gap to pull into after overtaking, so I don't feel like that can really be blamed on people hogging the middle lane.

Boy racers don't "automatically resolve themselves" through gaining experience. Without intervention you have to rely on reckless drivers gaining maturity, which is far from guaranteed, or having an accident that kills them or scares some sense into them, neither of which is desirable. The interventions currently are things like police catching them, which again is not desirable if an intervention earlier could prevent it escalating to the point where police have to get involved.

But my point is really that there are options to improve safety of younger drivers. If you want to reduce road deaths by 100, shouldn't you target the group that is causing the most accidents, and the most severe ones too?

Morbidly you could just as well argue that the elderly are going to die soon anyway so the issue "automatically resolves itself" in the majority of cases too.