I don't think compilers are a good example. The economics of software development has won a long time ago. For example in Gamedev with well known soft real-time requirements people (mostly) stopped doing that machine code dance many hardware generations ago. Like it happened with memory optimizations: people measure memory in GB now not in KB =)

I am sure programmers cherish every case when they can do micro optimization but in the retrospect the high level cuts is what made the system fit the perf or memory budget.

1) luckily, nowadays compiler's bugs surface very rarely, as the average programmer does not have capability to solve such issues

2) unfortunately, LLM's, by their very nature (not having a model of what they do, are prone to introducing subtle bugs, i.e. it is like programming in high-level language whose compiler likes to wing it