1) the room largely determines how any system at any price will actually sound
2) those with a goal to get the best sound possible will care and others less so
3) some rooms may require little or no tweaks for acoustics and others may be a total disaster. I have measured and tweaked acoustics in 5 different rooms in my house and they cover the range from little or no tweaking needed to well short of a total disaster but some serious issues to address to make things sound their best.
4) trained ears may suffice in some cases but to get it right for sure it helps to measure what you have first before taking action
5) Everything in the room affects acoustics to some degree. Room modes in the bass region are the toughest issues to address completely but some combo of traps and DSP can be applied to make things better. Other specialized room acoustic solutions like panels, etc. might be used to address any issues that cannot be solved in a particular room otherwise. Start with primary reflection points on walls, floor and ceiling based on speaker and primary listening location, Dispersion pattern measurements for a particular speaker model can help determine how to best apply, if needed.
6) DSP including room correction features in your system are your best friend when it comes to tweaking any system as needed to correct for issues associated with room acoustics!!!!
7) These days vendors integrate DSP into hardware (example:miniDSP, Anthem, NAD, Arcam, others) and software (example: Roon).
8) Once that is done (addressing room acoustics) you might then take the next step and tweak the sound from there to personal preference. Or just forget about room acoustics and the complexities of addressing those properly and just DSP to personal preference away as needed, for example using graphic or parametric EQ capabilities in DSP like that available in Roon. Either way (done right) should land you in a better place regardless of how good or expensive your gear is otherwise.