I believe it may have been deliberate. Yes, the loudness and tone controls us older folks used in the 70s were crappy circuits with crappy parts. So throw the baby out with the bathwater? Really the beginning of the sham that high end audio has largely become today.
In comes high end marketing. Knowing that few had the knowledge, skills or flexibility to optimize listening/speaker position and acoustics (I agree with a few posts above; if possible those parameters should be optimized before applying equalization or room correction), in comes the marketing nonsense; use expensive wire/coupling/isolation as tone controls or better yet swap out components and speakers in a circular audiophile dance that has made more than one audio manufacturer/distributor/dealer wealthy. Of course, none of that is a cost effective solution, more like polishing a turd.
Like I said earlier, this is the dawn of a new age. Ignore the marketing and high volume e-commerce salesmen (you know who they are, each has at least one full page ad in Stereophile; who do you suppose pays for those?) and use your own ears and brains.