I have concluded from experience that there are things that I cannot hear. I don't hear differences in dacs or digital cables, or power conditioners. I don't hear jitter issues from digital sources, network switches and cables, or streaming devices, or distortion issues associated with feedback in solid state amplifiers. I don't hear the special magic in analog sources such as tape or vinyl, nor do I detect euphoric distortion from tube amplifiers. I don't hear differences from power cables or other expensive cables.
I'm not going to argue about whether other people hear these things or not. I only know with confidence that I can't hear them.
What I'll claim I can hear clearly is shortcomings with the phantom center image when using only two speakers for stereo playback. Others claim they hear no problem with this in a properly setup system, and feel that it actually sounds superior to multi-channel systems or setups that employ some kind of inter-aural crosstalk reduction. I believe them. It's hard for me to fathom but they say they don't hear a problem even though they can hear all kinds of things I can't hear.
I've been in a lot of showrooms over the years, several HiFi trade shows, and listened to high end systems in people's homes. To my ears, straight stereo two speaker playback ALWAYS has a particular sound to it, a degradation of the tone of center panned sounds that's unmistakable. It's a particular effect, and like Amir says about dipole planar speakers, I find it tiresome.
So that's my problem. I have to deal with it. Those who don't hear it as a problem are lucky because they only have to buy two speakers and don't have to find a way to do any up-mixing. On the other hand, I'm lucky because I don't have to fuss over cables, dacs, streamers, power supplies and analog sources.