People also just drive a lot more today than 40 years ago, in part, because jobs and shopping are further away (it’s gone down since COVID due to more WFH). A car with 100K miles on it was an old car. Now it’s not unheard of for people to put that kind of mileage on their car in under five years. I have no argument that vehicles are much more well built today.

Well built for specific uses, but not necessarily well built to ensure lots of them are on the roads decades after their release.

As I said in another comment, I’m not arguing that cars are more capable of being on the road, just that I don’t believe people are going to choose to drive a ten to twenty year old car in 2035 - 2045 as much as they had fifty years prior.

I partially agree with but for different reasons that you're stating.

You could put less than $1,000 into a 100k mile car in the 90s and expect to get another 50k+ out of it. At least, I can confirm that that’s what I did with my 1976 Ford Elite and later my 1980 Camaro.

That 1980 Camaro was a far simpler car that modern cars. Simple generally means more repairable, but that comes at other costs. Economics have shifted this behavior in western society. In 1980 labor was cheap and simple machines meant lower skilled workers could accomplish the work too. Meaning when your 1980s Camaro was slipping out of gear it made sense to take your Camero to a transmission shop (do those even still exist now?) and have them do a full teardown of your transmission and get the synchros replaced. Today it is almost unheard of to get transmission work done and instead your Auto Technician will simply replace the entire transmission if any problem is occurring inside with a synchro.

Further, that Auto Tech will also be part Electronic Technician with knowledge of hydraulics, air emissions, HVAC, and more. That makes for a much more expensive labor per hour charge.

Moreover, there’s nothing aside from the maintenance of the vehicle and maybe improved gas mileage that would deter anyone from choosing to drive an older vehicle. There are far more reasons today to not choose a ten year old car than there were 30-40 years ago.

Passenger safety and crash survivability has improved dramatically from cars 30-40 years old.

Automotive emissions were in their infancy 40 years ago, which is a partial cause for the climate change we live with today.

My point is about consumer choice and the advancements of technology. Will people choose to drive vehicles that aren’t compatible with future technology.

I've driven old cars. Things start to break that don't break on even moderately old cars. Rubber seals on all kinds of things deteriorate. Rust claims the structural integrity. Long mechanical wear has you doing repair after repair always bracing for the next expensive thing. Its no panacea .