I do not understand why one would spend $x on audio gear and not, at the very least, spend 2-3 days with REW, listen and measure as to extract everything out of your room and system.
Thanks for the well thought out post. I'm not sure I can respond with a reasoned answer. The only thing I can say is I learned a long time ago that you can't make a deficient loudspeaker do what it physically is not capable of doing. So electronic correction has its limits. I also like clean simple systems so adding ANY device into the signal path has a downside. Then finally, I've been doing this a long time and even though I use trial and error, I usually stumble upon a workable solution in the end. I'm not against measurements, I just find their usefulness, in home audio systems, very limited.