Cars are getting increasingly more difficult to work on yourself, regardless of manufacturer.
Early, purely mechanical cars were easy to work with, there was no magic, everything which made the car work was removable, tweakable.
Then came fuel injection. It was a mish-mash of incompatible technologies and everyone doing their own proprietary thing. The gov't mandated the OBD and OBD-II standards into cars to allow independent servicing of the car, primarily for emissions reasons. For a while, things were simple again, since you could do basic interfacing with the cars yourself, clear codes, etc. The actual ECU maps weren't readily available, but easy enough to reverse engineer since you could memory dump the ECU through an exposed connector or even through the OBD-II port.
Then came air bags and auxiliary safety systems. These were locked down and not subject to OBD rules. To reset the air bag light after fixing a bad connection requires dealer-specific tools, an independent can't do it without acquiring these tools, which are usually prohibitively expensive, or simply not available.
Today, ECU's are encrypted, impenetrable, and export the legally required minimum OBD-II spec, and that's it. You usually have to take it to the dealer for any proprietary codes. As for tuning A/F maps, forget about it.
Some cars have huge enthusiast communities, so some ECU's get cracked, or you replace the ECU with a completely open one, but then sacrifice lots of the vehicle's features.
It's getting more difficult to be a weekend garage mechanic. Brakes and suspensions are still easy, but the engine is becoming impenetrable. A recent BMW, in which all I did was replace a dead battery, required a trip to the dealer to "accept" this new battery. The battery monitoring system threw a code which an independent can't clear.