Are trophies a measure of progress?

I consider them a measure of success but not progress. Put it this way no one would pick out a few good results from a league season and claim it shows progress if the rest were awful results. That's exactly what can happen in the League cup, it's great you get a trophy for it but its still a small sample.

The only real marker of progress out of a cup run is in building a winning mentality.
 
They are a measure of progress, but depending on the cup, that progress might not take you up to where you want.

Just as you can go from 5th to 4th to 3rd but never win and go back to 4th, rtc
 
I mean it's obvious that progress is determined by performances over a season. Trophies are a bonus and can be a sign of progress, but they're not by themselves. United's FA Cup run is the equivalent of Wigan's back in the day, let's face it. It wasn't progress, it was a great and lucky run. The season before, with the League Cup, showed progress
 
Cups can be fluked, always. Progress for a previously massive team and serial champions has to involve advances towards winning their league, which means at least being really involved in the race to the title until the last match, and ideally winning it once in a while.
 
No one takes the League Cup seriously until the semifinals. Your FA Cup came after you came this close to probably one of the worst defeats in your history in the semis.

You can luck your way to a cup trophy if you play decent enough from time to time, even in the CL if the draw goes your way. But the league and the performances in that league should always be the reference. So no, most trophies are not a measure of progress.

True. See the bulk of your European Cup successes.