Yeah as long as you ignore the engine (ECU/PCM/TCUs) in cars in the 80s, they're quite simple. Go back to the early 70s-before and it's mostly all analog or trivial electronics.
This was the video that earned my sub. Even though it covers stuff I mostly already knew, it's done in such a way that that it breaks down the whys that may not be apparent to people without a background in this stuff.
This and the video on hybrids, are, imo important works, because they break things down in a way that disarms tribalism, and explain how it is that we got to where we are. There are very real stakes in ownership, right to repair, and freedom of movement that rest on people having a good baseline understanding of this stuff.
Even as late as the late 90s, probably into the mid 2000s for manuals. The complexity of vehicles from that era is mostly in understanding the role of the sensors (or that they even exist in the first place). Once you understand that, they go back to being pretty straightforward. I guess the exception here is probably immobilizers.
The complexity of modern vehicles comes down to software coupling between the systems, which (to my knowledge) started with automatic transmissions, and then spread to everything else. In very modern vehicles, even the sensors register with the ECU and communicate on encrypted channels.
The reason for these measures is ostensibly security and quality, but automakers don't seem to mind the fact that it also makes many repairs more difficult or impossible.
