Older vehicles were "simpler" in the sense that they could be worked on easier. But, they required a lot more maintenance, didn't last as long, and broke down more often.
On a new vehicle, a tuneup might consist of replacing spark plugs and coil boots and an air filter
To use my old 77 F150 for an example as on older vehicle....a tune up consists of replacing plugs, wires, cap, and rotor, setting points gap and ignition timing after replacing the points and condenser, replacing the air filter, setting choke pull-off and tension, settings the idle speed and idle mixture, and float level too, depending on how I'm feeling. Oh, and I might crawl underneath and adjust the bands on the transmission, too.
Now, I can do all that at home, with basic hand tools and knowledge, but it's obvious that one vehicle requires a lot more care, and has a lot more fail points.
Not to mention newer vehicles are almost universally faster, handle better, make more power with less fuel, stop better, and are far safer. But, older vehicles will always have an edge when it comes to styling. New vehicles are ugly.