I can understand your thoughts regarding the UU not being the most organic amp and to some extent I can agree that it is a bit synthetic sounding but near as processed/synthetic/filtered sounding as something like Engl, KSR(Orion), Diezel. Next to a Wizard, old Marshall, Naylor, Peters, list goes on-on-on-sure, not gonna be near as open/organic...but I don't think it was meant to be that. What is does is modern hyper aggressive balls out metal and it does that in spades IMHO. As far as lacking richness/warmth...I'm lost with your feelings on that aspect, maybe the EL34 version is that different from the KT88.
The KT88 HPV UU I have is one of the most rich/thick/juicy/meaty saturated gain structures I've heard with great warmth while being insanely cutting with wicked attack. Can get that wicked low mid chew Bogner's known for the way I set it but also has a unique upper mid grind/attack. Is it modern sounding...well...it's named the Uber Ultra...LOL! But for being such an insanely modern, aggressive, cutting, thick, saturated amp, I feel it still offers great warmth for the amount of growl/grind/attack it gives up while remaining crazy articulate.