Cars have started becoming harder and harder for home mechanics to repair already from early 2000s, and that's definitely not a good thing whether you like or dislike cars in general. Making things harder to repair doesn't reduce them, just increases waste
Early 2000s? Try mid 70s. That's when all the electronically controlled stuff and emissions sensors came in. Pre-emissions cars are dead simple to make work.
The more primitive electronics are still pretty easy to work on and fix though. OBD helps with diagnosing, and the sensors are usually simple enough to swap out for a new one if they fail, in most cases. If an ECU fails, that's usually as simple as swapping a cartridge, like on an old console.