The machinery we build is more reliable than ever because of improved manufacturing tolerances, CAD stress analysis, better understanding of materials, etc, but manufacturing isn't perfect and materials aren't perfect.
When you add more complexity, you add more opportunities for failure, that's just a fact. Twin engine airplanes have twice as many engine-out emergencies as single engine airplanes.
I have the perception that 10 speed transmissions are less reliable than four speed because I've messed with the innards of both. There are size and weight constraints in cars, and you have to get those 10 gears into similar space where you used to get 4, particularly in transverse applications. Transmissions almost never fail due to the gear set failing. What happens is that some chunk of a clutch plate breaks off and causes havoc, or some solenoid gets weak and allows for clutch slippage and the clutch plates overheat and damage the fluid, which cascades pretty quickly. Big rig transmissions are seriously big and heavy duty, car transmissions are dainty things by comparison. Your Getrag example is an exception - it's a high performance transmission meant for expensive cars. Yes, once cost isn't a constraint, things do get beefier and more reliable.
My point was that the complexity of these things makes it very hard to fix them, so cars reach end of life sooner. You could have Jimbob's Local Transmission Shop rebuild your transmission in the past, now Jimbob is over his head. He has to send it out to a rebuilder, who will charge several thousand dollars for this thing, so it's only cost effective to fix cars which are relatively new.
Turbos are used to make smaller engines behave like bigger ones, they help generate more heat and more pressure to develop more power, but weight and size are still constraints, so everything operates closer to maximum stress tolerances. I've been racing cars for almost ten years, and on hot days, it's not the naturally aspirated engines which blow up, it's the turbos. As with transmissions, big rig turbos are not constrained by size, weight and cost like passenger car turbos. They have gotten a LOT better, don't get me wrong, but a turbocharged engine is a much more complex system than a naturally aspirated one.
In my opinion, the sweet spot for technology/simplicity is behind us. Cars built between about 2000 and 2010 have simple port injected engines, very good engine management systems which result in very clean emissions, and generally no turbos. You can cost effectively keep one of these things running forever, and what happens is that the body and interior fall apart before the engine quits being cheap to maintain.
I'm a car guy, I love working on the things and hacking on engines and ECU's. Don't get me wrong, I think new cars are wonderful, but they're becoming tightly integrated systems with little in the way of user serviceable parts - throwaways like cell phones.