I liked your posting!
Since I was never graciously skilled with mechanical wizardry... that did not stop me...in previous years I have attempted many repairs to appliances in the home; and as I think of it now - some of my cars I owned in the 70's, 80's and 90's... once we got into the 2000's - I was making a decent enough income to let the mechanics "get er done"!
My brother used to laugh and joke, at times, I could "screw up a 1 car funeral procession"... sometimes true, most times I was quite "fulfilled" in my accomplishment of a repair!
I have a good management job. Having worked my way up through from production to automation programming and industrial robotics specialist. But I was wrenching on things for fun as a kid. Broken saws and mowers and motorcycle people would give me. Vacuum and radio/TV as well. Very rarely did things ever work after I touched them though. Lol. Eventually I got some success in my late teens with a few repairs. After going into the work force in the early 2000s I kept wrenching as a hobby (and a way to afford to race bikes and cars....broken ones are affordable, good ones werent) and my hobby became a side income. Now I restore and build a few and maintain several at my shop, even have employees working there while im at my real job.
And a lot of the "GOOD OLD DAYS" of classics weren't all that great either. Plenty of the old cars had parts that you simply couldn't get to, just like current ones do. The old big block mustangs come to mind. Any of the 70s and 80s vans with the motor halfway under the firewall were awful as well. Very rarely did anyone have working rear drum brakes. They are most often not adjusted and never hit the drum and about half the time the parking assembly and equalizer are gone altogether. Early fuel injection, GM TPi, Bosch systems, early computer controlled ignition all sucked and died for no reason. Duraspark 1 was awful, duraspark 2 was probably worse....
I started working on the 80s and 90s mustang and camaro/trans-am. That's what I learned on. (And they are still in automotive purgatory where they had enough computers to piss off old guys but too old to have interface for the new guys) And thats how I got where I was going when the wife was in college. Once she got her degree we bought new vehicles and have kept at least 2 since. As hers wore out we kept them running for errands or gave them away. so I learned how to work on those. Tpi, mpfi, sfi gdi, turbo. I work on several diesel but that's one area I need improvement on. Then I got a few classics and restored and worked on those. People started bringing me ATV, boat, Tractor and everything else. Small engines (I hate small 2 cycle.... no room for anything).
Assuming I can get parts (decent parts) I have no fear of any vehicle. Ive pulled hundreds of engines, the oldest from the 50s trucks to the newest one ive pulled was a 2018 STI.
They are still the exact same principle. Before you had no way of knowing why or what the engine was doing. Now you have 1000 parameters and sensors to tell you (assuming the sensor don't lie, you have to watch that) if I wanted to know what my 66 big blocks AFr was I'd have to hook my air fuel meter up, one on each exhaust. Then I'd have to pull the choke and let it warm. Then I'd have to datalog at every rpm AND at each stage in the carb process. Adjust the metering rods. Then the step springs, the accelerator pump or power valve etc etc. On a new one I simply plug into the obd2 port and watch the AFR lambda for bank one and bank 2..... if one needs adjusted I do so simply in the afr table but the computer will do it all for me so it won't
If I think there is a timing issues on that "good old" car I have to pull all 8 plug wires. Wire in an oscilloscope (historically a machine the size of a tire changer) i have to measure the dwell and timing, with a timing light and dwell meter. I have to disable the vacuum advance and verify the cap and rotor are OK and the hold down is tight. Then I can start it. Assuming base timing is ok I can then rev the engine slowly to see how fast my mechanical advance is coming in and adjust that with weights and springs....then I can determine if I need my vacuum advance to ported or to manifold vacuum and hook that up and see how much vacuum advance I have and add up all the advance. If I need to adjust the total I have to weld up the advance plate by removing the distributor and disassembling it to remove the massive advance that early emissions police mandated.
On the new one I can simply plug into the obd2 port and go to the ecm/pcm and view live data and see what timing is doing and if I don't like it, change it with a laptop on a table.
I have at least a little bit of knowledge on the two and I'd rather work on the new one anyway. More specifically id say in order
Most cars from 2000-now
Most cars from 79 and before
Most cars from 80-2000
Anything German (and most italian) from 80-now. Lol.
People claim the new ones will absolutely make you mad because of placement but some have always been that way. Someone comes in needing a starter and on most cars its a 40 minute job. On a Toyota truck its a BIG job under the intake. Same for a Northstar. Some like the Honda 2.4 its a real pain because of the fwd and exhaust manifold. Some like the old 2.8 GM it was A pia because once unbolted you had to jack the motor up to remove it. Even the later 4.3 4x4 s10 was a pia to get the starter on. I remember a Pontiac starfire I cussed the started on for a whole day. I don't even remember the issue but I remember I said I'd never do another one. Never even saw another one. Lol. You can change the injectors and plugs in a Ford v8 in 30 minutes. Its a day on some Toyota to get to just 3 of them.
So yeah some new things (ANY heater core after about 1980) will be a huge disaster when they didn't have to be so bad but that's been the case on vehicles for as long as there have been vehicles. "Great ideas" like reverse threaded lug nuts on one side of the vehicle (thanks Mopar) and oil filled alternator mounts (thanks BMW/VW) have always been the case.
But its case by case/ model by model. Not really decade by decade.