One would think after 117 years of evolution (1904, invention of the
vacuum tube) and with only 4 other components involved (R, C, L,
transformer) engineers would have reached the optimal configuration for a
tube amplifier by now.
But there’s another ’science’ involved. It’s called Marketing ... the art of tempting people to spend top dollar.
Ya- you'd think. They've been making automatic transmissions for a while too, and yet they still fail in the middle of nowhere.
There are actually innovations still occurring with vacuum tube amplifier tech (I can call out a couple of patent numbers if you like). Electrolytic caps keep getting better- and the better they get, the more effectively you can bypass a power supply. Plus we have computer modelling now so you can simulate and optimize circuits (including tube circuits) better than you could back in the days of slide rules.
