I don't know a huge amount about language design, compiler implementatin, etc. However, a personal anecdote - One of the bigger surprises for me when I was beginning programming was that better hardware couldn't compensate for my flaws as a software developer.

I created a script that migrated data to a new system. The script took 48 hours to run, and we needed to do it over a weekend. The lead dev was unhappy with the performance. I suggested we just use a more powerful machine, and he gave me permission, but said it wouldn't help. I can't remember the specs of the machine, but it was double/triple as expensive as the original machine.

It improved performance only marginally. I went through my scripts, and started to debug it, looking for problems. Optimising my scripts easily doubled or tripled the speed.