Hi Ken,
More than twenty years ago, after years of graphic EQs, I worked on my first mixer with fully parametric EQ on each channel, a Souncraft Ghost.
It was like a breath of fresh air blowing in the room.
These days I use the graphic EQ on the Mackie mixers only when a filter happens to be right where I want it frequency-wise, and the filter shape is reasonably useful, and I have other uses for all the parametric filters.
"I would like to be able to turn only that frequency that is feeding back down."
I often work with old time bands, playing in A. With five or more instruments wailing away on A, 440Hz can be an issue, as well as sometimes 220 and 880.
With a graphic EQ I have a choice of pulling down 400Hz or 500 Hz, that is quite wide and impacting other notes around the problem.
With parametric I can go to exactly 440 and put a narrow filter on the Fiddle, Banjo, Mandolin, Guitar, and/or whatever else is causing an issue.
Early digital mixers didn't have graphic EQs because each filter takes so much processing.
Even with the processing Mackies have now, adding 16(or 32) channels of 30-band graphic EQ could actually be quite demanding.
I'm guessing that the more familiar you get with parametric EQs, the less you will appreciate graphic EQs.
Thanks and good health, Weogo