I agree... But if you are familiar with the components, one can usualy have a good idea of the effect and if it is likely to be a good match. So, if you’ve got a very precise sounding system and add... say a very analytical DAC... it’s likely to push the system too far. Or if you have a very warm organic system that very analytical DAC it is likely to sound good... adding needed detail.
I’ve seen some folks here with a complete mixture of components... and though, great combination of warm and cold... and they loved them. Also, some folks with a string of highly detailed (far more often) analytical sounding components that they complain about... fatiguing, or causing sibilance, or they just get tired of listening.
So, I definitely agree... but one can often predict the likely outcome if you know the components.

