my view is slightly different, in that there always has been good, and not so good in both amps and speakers, and times have changed but good kit is good kit.
i have quite a collection of vintage hi fi, 20+amps some working and others not, about the same in speakers,decks, lots of drivers, and nearly every audio valve.

my first valve amp was out of a german radiogram, it sounded ok.. but it got the full treatment over a few months,
changing the volume control and shorting out the tone controls, took away the vintage 'cloudy grey' sound,
changing the coupling caps then transformed the clarity,
then lastly i replaced all the carbon resistors for modern quality components,
that gave the modern sound... clean and detailed

i never went back to solid state amps after that amp.
vintage warmth.. not for me.. thats about old components
pete walker knew his stuff, but he had a product.. esl57's and quad 11's they work very well together, and made a very nice sound
i have peter walkers earlier speakers and have owned a good pair of 57's and quad 11's,
and i must say i really liked them both, but prefered the earlier speakers (which where nearly double the price).

as stated, shop bought hifi is made for a profit.

with all the amps i own,some really good ones, i still use diy amps,
but to be fair, the bits used to make them, cost much more than many bought amps.
the trouble with hi fi is there is no right, what may seem an fantastic sound for one person is ok for another. the only way is extending listening to lots of kit, the differences then are apparent.. sometimes.. for some folks

steve