The point you are missing about cars is that in many ways they are a lot more complex now than they ever were. Most modern cars now have electronic engine management systems which are way beyond the amateur mechanic to service or even to diagnose problems. While service intervals are typically longer than they used to be, this is all to do with advances in oil technology combined with more reliable electronics. Improved reliability has come from the same improved manufacturing techniques with better tolerances that has seen us move from 5/6 speed to 11 speed. Beware the advent of electronic shifting and the impact on the home mechanic.