I don't have experience with vintage equalizers, but I have this 15-band dbx 215s ($189ish) in my music room.31 bands is pretty large. I can't say I've compared one of those but I have switched in dozens of lesser band EQs like ADC, Technics, Yamaha, JVC and even the cheap Fishers of the mid 1980's where not all that bad. I've AB'd the ON/OFF states and have not heard any change in sound quality when they are flat or EQ'd and the improvement with EQ is so large I am surprised you dislike them. I've met and talked with many people who believe a EQ/tone control ruins the sound but they can't explain why but they heard rumours and reacted. I'm a EQer for sure but not with cheap stuff that does induce hum/buzz/fuzz and I've never heard a decent EQ cause that too.
I was paranoid about adding a ton of distortion -- because that's the first thing everybody says about analogue EQ -- so first thing I did out of the box was spend some time A/B'ing it by setting it to flat and engaging/disengaging it, with and without music playing.
My conclusion was that it was inoffensive to my untalented ears. I don't doubt it has some impact on THD though. If I wasn't a selfish jerk I'd offer it up for measurement... @amirm, any interest in measuring it?
https://www.guitarcenter.com/dbx/215s-Dual-Channel-15-Band-Graphic-Equalizer-1294516231293.gc
You cannot cascade 10-31 opamps without a serious noise penalty.
Obviously not a product for Mr. Restorer John, but on that note, when I had the Schiit Loki I thought it was neat. Only 4 bands of EQ, so "theoretically" not a major distortion machine. 4 bands sounds restrictive but it was pretty useful: 20Hz, 400Hz, 2kHz, 8kHz.
I basically used it for loudness compensation, to dial up some more bass at low listening levels, or to cut the bass so as not to piss off the wife at night. Sometimes an analogue dial is just 100x more convenient than digital.
My only real gripe was the price ($149USD, yowch...$38 per band!) and sometimes I felt that that a 60hz adjustment would have been a lot more useful than 20hz.
JDS Labs has a similar model, with only 3 bands instead of 4 for those who feel Loki simply offers too much functionality hahaha.