OP here.
Each to his own, but my take on things is as follows:
Very old recordings certainly could use a little tweak in the EQ - eg Robert Johnson's blues recordings from the 1930s
Even in modern times, sometimes the sound that came out of the studio is not even what the artist/band intended! I have had many musicians tell me this, eg one artist told me when buying his CD at a gig "you will have to turn down the bass on this CD to make it listenable, they messed up this recording good and proper!".
You can listen to different albums by the same artist/band and notice striking differences to the sound balance - brighter, thinner, warmer, more bass etc. Exact same band but different recording studio, different producer, different sound engineers, different mastering etc etc. Every step changing things slightly - and not always in the direction the actual artist would want it! You might say "well that is what the engineer intended to do", but surely it is more important that it reflects what the artist wanted it to sound like?
And then there is the argument that, as a consumer of the music, you have the right to listen to the sound as you yourself wish to hear it. You may absolutely love the music/songs, but really hate the way it's recorded. You still want to listen to the music, but need to tweak the EQ to make it listenable. The artist would rather you bought his music and did that, than not to buy the music.
Perhaps other people only listen to modern recordings by Ed Sheeran and Adele. I have over 3000 CDs spanning recordings from the 1930s to present, and nearly every music genre under the sun, including recordings done on a shoestring by virtually unknown acts. There is a huge variation in quality and balance in the sound of the finished recording. For me personally, I like to be able to tweak the EQ if I feel the need to. But the rest of the time, leave it flat.
Lots of people who shun tone controls on amps change their cables (interconnects and speaker cables) to change the sound of their system - they are really just doing the same thing!
A final point. Some of we older music & hifi fans have some age-related hearing degradation whereby we do not hear the higher frequencies as well as we used to. It's good to be able to give the treble/highs a small uplift to compensate if need be!
