I think you might be confusing "measure" with "observe". Measure in this discussion has a distinct quantitative implication.
You've never had one steak you prefer to another without doing quantitative analysis on it?
I love making cocktails and I can definitely tell better from worse, noting qualitative differences (a bit dry, too sweet, mouthfeel a bit thick) with absolutely no quantitative measurements involved.
I can certainly tell the difference between a good and bad violinist without measuring anything.
From a different perspective: many of my favorite movies have a 3.5 star rating on Amazon, in this case the measure does not correlate well with my sense of improvement.