I never noticed a big difference when using Yamaha's YAPO Room EQ, but I would never call it snake oil.
Unlike so much junk in audio, room correction is logical. Room's color the sound due to frequency response issues, and addressing that issue holds the promise of higher fidelity sound.
In fact, EQ is where sound issues SHOULD be addressed. People mixing albums most certainly apply EQ to make the mix better. PA pros in venues most certainly apply EQ to try to make sound better. EQ is a tool which has the benefit of improving sound.
I would go as far as to say that the audio ideal of a flat response is flawed. Our hearing is not linear. Room response is not linear. Speaker response is not linear. The mix was damn sure altered to someone's taste. So applying EQ (for all sorts of potential reasons) is in no way some horrid sin, IMO.
To go off topic (sorry,) I feel the need to relate an anecdote. During a recent listening session I realized 70s classic rock often has unpleasant mid bass. On some songs bass was boomy, and unpleasant. What would be wrong with using EQ to tame that a bit?