I can hardly imagine all speakers sounding the same if equalized to flat. It's how a speaker releases its notes that gives it its own distinctive sound, whether you enjoy it or not. Room reflections and acoustics are, of course, important.
But speakers in rooms are usually far far from perfect. The first thing to musical bliss is taming the bad bass nodes and room issues, and if the speaker is contributing to that it gets corrected as part of the process. With a tiny bit of lowering excessive spots in the upper bass and some high treble my goal is the very flattest response in room in my chair from 31Hz up to 12Khz (usually +-2dB). And that's no sub. Taking the irritating bass bump 80-160 from the Raidho D2s is a very good thing. After that it's liquid music in your ears, and a flat response.
Taming the room and speaker into a nice flat response allows the true beauty of the sound to come through. The additional clarity and tight bass is a no brainer. Those who still disrespect any room correction may never have tried with the right unit. I'd never go back. DSP gives me far better sound, always.