I'd say many of those switchable things end up being pretty subtle changes that ultimately are "eh, just park it to one setting because it sounds best that way". I see them as a different thing than doing something like "my guitar sounds too muddy so I cut the low mids a bit", which you often can't do because the 3-band passive EQ midrange control is not doing the thing you'd need.
I think this is way too difficult to generalise like that. Some switches are subtle, some aren't, but there's no correlation or trend with that. There's simply too many being used for any number of things.
As far as having different kinds of controls to address different tonal problems, I think there has been lots of different approaches across different circuits, and things just end up back at a simple passive tone stack because its simple and it works. Even with that, there are cathode follower vs plate driven, placing the tone stack in different parts of the preamp, having the master volume before or after, different tone slope values, different pot values, different tapers etc.
There's so many moving parts beyond just the amp that trying to solve every part of the equation with amp controls is going to lead to something crap. If my Fender Champ sounds like ass with EMG's, I don't really want more complex controls to address it, its just the wrong choice of gear. The limitations of simple circuits are just as purposeful and considered as amps with lots of controls, and generally I think the better design is the gear that has less controls. That's not being stuck in the past or traditional, its just good design being good design.
I feel like most tube amp manufacturers are very afraid to make anything different. I'm not talking about making amps that have a wholly original sound - we guitarists don't generally want that. I'm talking more about how to make e.g amps that can reach the sounds we want with more flexibility or practicality.
This makes me think you're being willfully blind to the trends of amps over the last decade. Tell me an amp from 30 years ago that's lunchbox sized with some kind of power scaling or reactive load, and IR's and digital FX. Surely these are the kinds of innovations in flexibility and practicality you're talking about? basically every single new amp design features at least some of these, if not all of them. I'm not personally interested in Marshall's studio series, or a Fender Tonemaster, or a lunchbox ENGL, or anything Victory make but thats where the new products and focus is. What year was it that Marshall made an amp with a digital modelling preamp with a valve poweramp? and it was actually good! Amps are more flexible and practical (as in lower volume if you want it, and portable) than ever. This is 100000% a modern trend and likely sells significantly more than big loud dinasaur amps. Most companies offer lunchbox versions of their amps these days.
Keyboard players embraced MIDI and modularity, bass players embraced solid-state/hybrid and more complex EQs, but guitarists somehow had this "anti-tech" movement where people went from those MIDI controlled refridgerator racks back to pedals and combos, with no in-between solution that combined the best parts of those until digital modelers got better.
I think from the rack trend, we moved towards more complex switching amps. Mark III vs Mark IV, SLO100 vs Dual Rectifier, Diezel VH4's and JVM's vs older Marshalls. These have pretty advanced switching internally to do some pretty complex combinations of circuits as well as better FX loops and features. There's even unique concepts like Diezel's VHX, Marshall's JMD:1 etc.
Prior to Kemper (which is basically a modern tech that guitarists have embraced) the advanced complex stuff were amps like JVM, VH4, Mark IV, Triaxis, as well as the earlier digital amps (which people definitely used - POD's and Vetta's and Flextones all sold an absolute truckload).
I don't feel like I've even scratched the surface of new tech that has come up in my lifetime for guitarists - it feels like a constant stream of tech, some good and some bad, but I don't see it as regressive just because you can still buy a Plexi or Princeton still.
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