The aim with room treatment is getting the right balance, not killing it dead, and is quite unlike adjusting the beat timing accuracy or tone accuracy of a recorded piece of music!
Positioning of speakers and listener are key factors in setup, more so in some room than others. Narrower dispersion speakers will reduce side, ceiling and floor reflections compared to wide dispersion speakers though possibly reducing soundstage and size of ‘sweet spot’, and toeing well in will reduce side reflections, though if side walls are near then there will still be some early reflections to degrade the sound and neither of these choices will reduce early reflections from a near wall behind the listener. If after optimising positioning a room has reflective surfaces close to the sound path or the listener then regardless of quality of electronics, cables etc some combination of absorption and scattering to stop the near reflections interfering with the main signal is likely to make a significant improvement to clarity and detail, maybe even tighten sharpness of timing.
If there are bass issues such as booming or cancellation at the listening position even with best positioning, treatment can reduce the effects and improve the sound, though unless mild it is highly unlikely to be feasible to completely cure.
All that said, the best sound I have ever heard from recorded music anywhere, any time, was from a system more limited than mine is now, played outdoors in the open - effectively removing all room effects. That to me was perfection, albeit that it would be even better with a more capable system. Also, returning to the thread theme the setup meant there could be no acoustic feedback to the source or electronics as they were indoors the other end of the house, and at least 100 feet away from the speakers, but I believe the lack of room effects was the most significant factor. Details in the thread What’s the best-sounding system you’ve ever heard?