Decent HiFi doesn't have EQ. No tone controls, no loudness curve, no bass boost. It doesn't need it. A great headphone fed with a flat response signal will sound great.
Headphones have less need of equalization, especially if you can afford a set with very tight quality controls. But Iheadphones don't present commercial music in the way that it was originally created. For that, you need speakers... and if you have speakers and a room, you'll almost certainly need EQ.
There are thousands of old 70s amps and receivers out there with phono inputs. The RIAA curve isn't rocket science. I remember when amps stopped having phono inputs, I had to get a phono preamp dongle from Radio Shack to use my turntable. I think it cost around[ $25 and did the job perfectly.
I have a nice old Rane 1/3 octave equalizer I use to EQ 78s. It works fine. Digital parametric equalizers are even better. EQ isn't an issue except with those old 70s five band cheapo units. They would hum and crackle and distort and generally mess up sound. It isn't like that any more.