It means that the average car buyer cannot buy a car within the time the average car buyer in the past could. Also it means you are likely to be making a large monthly payment in 4 to 6 years for a car that isn't worth much --- in the past when you could pay off a car easily in 2 years, you weren't making big payments after it lost it's worth. Cars today are not likely to last longer than cars in the past --- with all the plastic parts, they're likely not to last nearly as long. Plus don't forget the amount of the payment that goes just toward interest on the loan --- that's all money thrown away. Interest on a 2 year loan is less than on a 6 year loan.
Cannot. Really? You have any stats to back that up? Or is it just a feeling?
The average buyer probably carries a lot more debt than in the past. Doesn't mean his real income is lower.
Actually, it means that you have less disposable income than you did thirty years ago.