I was never quite sure why this was a thing back in the 60s but instead of guys taking showers my classmates seemed to like the idea of applying cologne to cover up their stink. I can't tell you how much I wound up detesting the stench of BO covered by Jade East.
My view has always been a simple one. Fixing the problem is always preferable to covering it up, though that's not always so easy. A bright tweeter can be tamed by any number of cover-ups which might make more economic sense than replacing a pair of speakers.
But, the core of the problem remains and it's a tough discipline to instill in one's self. Whenever I hear a system trapped in the speakers I first turn to setup. If setup doesn't release the sound from the speaker's grip we work ourselves back through the chain to find the culprit rather than start the great cover-up.
Quick fixes are always easier but usually less effective. This is one good reason I agree with my friend Bill Low of Audioquest in his mantra to do no harm. He and I both recoil at the idea of using cables as equalizers, yet sometimes there's little choice if you can't fix the core problem.
The first step in this process is as mentioned. Find the root cause of the problem. Once you've narrowed it to the culprit it's ok to mask the problem until you can figure out the best way to fix it.
If only I could have handed a bar of soap to those classmates so many years ago.