@Perki - I dabbled in audio about 10 years ago. I had standard, crappy, 18 gauge cable from Home Depot for my stereo system. I bought some cheap Focals - and was told to upgrade cables, and I heard nothing different. I was 30. I was almost abused by "objective" statements of certainty that these tweaks would come together to be better.
But they didn't. I was ridiculed for a crappy system. Or that I couldn't hear. I was discouraged, and thought, maybe it is me?
And it turns out - it's not me. My hearing, at 40 years old, is exceptional. My system today which is upwards of 30k, isn't cheap or crappy. Can I say I have plugged in 10k cables into my system - no. But have I tried tweaks, yeah. Did any of them work? No...
And, you raise a great point! It's not my money being spent if someone wants this vs. that! They can buy whatever they wish! It's the declarative statements made though, your system stinks unless you have product 1, 2, or 3 in it. That's where things I think go too far. Especially if it can't be objectively measured. Buy what makes you or others happy! But, i just ask they don't dump on others when they don't hear a difference.
I'll close this out with two thoughts. The first is a statement that "I don't hear as well, but I listen better." - that's akin to saying I can't taste as well, but I eat better. WTH does that mean?
And 2 - we do all agree that frequency response drops with age. But, thankfully, most music isn't above 10khz. But, it's isolating something - it's hearing that change, or where an object comes from, that too, is affected by age. (As we age, it's harder to hear in a crowded restaurant for example.) To the point of the OP - I think that's where things get harder to distinguish. And where I think statements being made with a lot of force, especially when it comes to someone new in this hobby, are detrimental to the hobby.
I don't know - but - if you're still reading this - i do look forward to your thoughts on it.