The collision safety regulations appear to have caused side and rear windows to get smaller (probably to improve side impact intrusion protection) and pillars to get wider (rollover protection).
Aerodynamic drag is a major contributor to fuel efficiency. To my eye there has been a trend (in Australia at least) to blur the line between sedans and hatchbacks. Sedan boots/trunks are getting taller and more sloped to smooth the transition from the rear window. The rear of hatchbacks have been also getting more sloped. Both are attempts to get a more tear-drop shape without overly compromising utility.
After many iterations working within the same industry wide constraints, it is not surprising that designers all optimise their designs to similar shapes and sizes.
The same effect can be seen in road bicycles. The UCI imposes limits on wheel size and other physical dimensions on bikes that are allowed to be used in UCI events (pro and amateur racing). Above 30km/hr aerodynamic drag starts to a major effect on the power a cyclist needs to output to maintain speed or accelerate. In recent years bike manufacturers have been wind tunnel tuning their designs more rigorously. This has resulted in the aero road bikes from the major manufacturers converging to almost identical designs. Cycling commentators and journalists have started agitating for relaxation of the UCI rules to try to get some innovation happening again.
I got a 47k mileage 1991 Mazda Miata for 4500$! And the girlfriend loves how cool it is and shifting stick. You should try to snag something from the 90s before people realize how nice they are.
Modern cars are spy machines needing constant software updates and nonsense features like "push button start" which is probably just a ploy to no longer have to make complicated ignition switches.
I think the 2010-2012 strike a sweet spot for what you're saying. Reasonable safety, not a lot of software.
Besides, if my girlfriend and I want to take a risk an enjoy a nice car I don't like the government telling me otherwise.
You're right about that date range, probably the best without software that thinks its better than you. Its going to be bad when cars have full electronic steering with no mechanics - you will essentially be holding an xbox controller and have no idea about your cars alignment lol