Tubes come with uncontrolled performance variables, whereas solid-state
devices vary, but only within specified limits. That's a real
distinction.
Not really! When you say 'solid state devices vary', you mean that they vary from completely nonfunctional out of the tape or bag or whatever they come in, to completely exceeding their specs so you can't find a match for them, right? I don't see that as particularly distinctive!
These days there are a lot of counterfeit Chinese semiconductors out there that don't meet important specs in any way, in addition if you look at all the obsolete semiconductors out there that you have to pay a premium for on ebay if you can find them at all (there are far more obsolete devices than there are that are in production), tubes can look pretty attractive; you can still find competent new 6SN7s and the like.
We're rarely had to match tubes to get them to work in our circuits, but when we involved semiconductors, we've had to build jigs to test them so as to sort out the devices that simply weren't going to work at all.
So I find this bit of your argument as simply a non-starter.
I get that for whatever reason you don't like tubes. I don't have a problem with that. We can cut with all the technical stuff since when it comes down to it, it does not matter. If you look at it from an economic standpoint, then you really see what is going on:
Tubes are still here after being 'obsolete' for longer than when they were the only game in town! Normally, when a new technology succeeds the prior art, the prior art becomes a museum piece. But apparently people want tubes and keep them going. The simple fact that the Chinese built a new factory to get into the tube game should tell you something- tubes aren't obsolete because they do things transistors so far can't (with the possible exception of the Static Induction Transistor, sorry, obsolete, n.l.a.), which is to be so linear that building a low distortion circuit with them is easy.
More to the point, tubes don't make the kinds of distortion to which our ears are finely tuned. Transistors do! This is why the tubes/transistor debate has been around far longer than the internet and won't be going away anytime soon.
