It's not a coincidence - new cars have turbochargers and electronic engine control that provide huge performance/efficiency gains and necessarily are harder to repair.
Your average shitty 4-banger from the 80s or 90s is not remotely comparable to a new engine - in almost every respect (including reliability!) the new one is better.
Yes, and who exactly is going to rebuild a $2000 engine instead of buying a new one?
The labor costs ALONE make that a horrible idea for anyone who isn't a mechanic already - and if an engine lasts ten years the depreciation on the car is intense enough that it doesn't matter.
Your average shitty 4-banger from the 80s or 90s is not remotely comparable to a new engine - in almost every respect (including reliability!) the new one is better.