In general I accept what you’ve written Marco and I have no doubt that in fact a great deal of Hi Fi component manufacturers do in fact listen to their products 
However, the designer still has to have an element of repeatability to his/her design and if some amplifier designer is prepared to contribute to this thread stating that each amp he/she builds is built in isolation from the last unit built (ie none of the specifications of a previous build are used) and the final configuration isn’t measured and recorded then I’ll have to take their word for it.
What I believe happens is, they may indeed initially design to a specification and then fine tune by listening but the changes have to be recorded and repeatable (?)and unless the designer has a phenomenal aural memory, they will build to a written and measurable specification finally, even if that final spec was established by listening and recording the changes that gave the required improvement.
Despite your views regarding Peter Walker and Quad amps they have a very high audiophile reputation so building by measurement and specification does at least seem possible even if you personally don’t find the results pleasing 
I’m not sure the “best” audio components are bespoke built Marco. I wouldn’t argue that there are some very talented people involved in “bespoke” audio but I suggest the really large companies with their enormous resources tend to rule when it comes to quality audio reproduction. Bespoke is cool, you get something individual and possibly unique. If you’re lucky you get value because the small manufacturer doesn’t have corporate overheads etc. This doesn’t necessarily translate into best sounding available and I doubt very much if it applies at all to equipment using newer technologies.
Single spur balanced Mains. Self built music server with 3 seperate linear PSU, Intel i5, 16 GB RAM no hard drive (various Linux OS). Benchmark Dac2 HGC, single ended XLR interconnects/Belkin cable. Exposure 21RC Pre, Super 18 Power (recap & modified). Modded World Audio HD83 HP amp. Hand built Monitors with external crossovers , Volt 250 bass & ABR, Scanspeak 13M8621 Mid & Scanspeak D2905/9300 Hi. HD595 & Beyer 880 (600 ohm) cans.
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.
-Bertrand Russel
John.