What you say is hilarious true for general anesthesia and was already deeply unsatisfying when I was a student decades ago. I think if GA was being introduced today, it would be have to jump through incredible hurdles to be used. In many ways, thank goodness these parts of medicine were discovered earlier when we had lower standards! :-)

I often used to tell my students that (plausible) mechanism is what distinguishes productive science. For example, population genetics was on very solid empirical and theoretical grounds but until we understood how DNA replication / transcription worked from 1953 onwards, genetics had a sort of unsatisfying magical, fairy-tale feel about it.

This is contrary to what some philosophers of science will tell you about measuring progress science purely in terms of its predictive power.

What I have to say applies really only to my fields of medicine and biology. I have no idea how physics or chemistry works as practical endeavours.