This is verifiably false with three minutes of searching, which I did on my cellphone as I sit by a campfire. As an owner of both a 1965 Mustang and a 2015 Explorer, the difference in size between these vehicles is comical. I've rented a 2020 Camry that was larger in every dimension. It got great gas mileage, but small it was not.
1967 Ford Mustang Length: 183.6" Width: 70.9" Height: 51.6"
2020 Toyota Camry Length: 192.1" Width: 72.4" Height: 56.9"
https://en.m.wikipedia.org/wiki/Ford_Mustang_(first_generati...
https://en.m.wikipedia.org/wiki/Toyota_Camry_(XV70)
The 1965 Mustang was even smaller and lighter. The 1969-1970 Mustangs, while larger, are still smaller in every dimension than a modern Camry. Some older cars were indeed boats, but almost all modern American automobiles are boats, and a lot of this has to do with the laws that regulate and shape the products created by the American automotive industry.
I'm not sure why you compared the Mustang to an Explorer though. I mentioned the thunderbird as being comparable to trucks, and those were well over 200 inches in the 60's. It's still an exaggeration to say that's as large as a truck with a crew cab in most cases, but the 209.4" length of a 1969 Thunderbird sedan is slightly longer than a Ford F150 with a regular bed size at 209.1". They were all, by most measures, much larger than their comparable categories today, and much larger than those categories a decade or two ago.
They still make the Mazda Miata, BMW 1 series, Toyota BRZ, etc. These are all small cars, although I'm not going to research all of their dimensions. The truth is there is a very small minority of people who want cars smaller than that, and it's not profitable to produce them.
I’m reminded of my grandparent’s 1979 Cadillac (Not sure of the model). It barely fit in the garage. They parked their Chevy Suburban in that same garage.
Basically, OP is "graciously" willing to give up his manual transmission if we provide him a car that suits his style and comfort at the expense of everyone else.
Luckily for us, he isn't able to find one.
And judging by their popularity, that's where a lot of people who may just want a little bit larger car are going.
It seems like a set of rules that locked the window and left the door open.
What alternate dimension are you from? My older brother had a 60's Ford Fairlane when I was growing up. My first car was a 67 mustang. I had a friend with a 68 Camaro. I knew someone else that had multiple Thunderbirds from that era.
These were not small cars. The Mustang and Camaro were the size of a full size sedan today , if not bigger. The cross sections of the doors were very large, they just aren't very space efficient at all. They're only small relative to the other cars of the era, and I wouldn't call their size reasonable in any real way.
Those are the coupes. The sedans, such as the Fairlane and Thunderbird? Those were about as big as a modern full size crew cab pickup.