I acknowledge there are varying degrees of quality. But when the spirit is based on tastelessness and neutrality, and there's so little difference between ok and good, what's the point in demanding quality?
It isn't based on tastelessness and neutrality, though. If you think of vodka as a generic thing to mix stuff with, maybe, but people do take shots of the stuff you know (and I should know, I'm Polish, we take shots of the stuff on easter morning

)
There is also a big difference between 'ok' and 'good'. Again, if you're just mixing it with stuff, you won't notice.
Enjoyment from vodka drank straight is lame.
Maybe lame from your POV, but you're not Polish or Russian
Other liquors have way more going on.
Sure, vodka is a bit minimalist, but so what? So is a cheese pizza, and there are good cheese pizzas and crappy ones.
I'm not saying you can't be a purist about your vodka's purity. I'm just saying that it's lame and you're probably wasting your time.
It's not about the purity, it's about distillation method, ingredients, general taste, and aftertaste (or lack thereof).
Then there are your flavoured vodkas, out of which my favourite is this:
It's a rye vodka, flavoured with 1 single blade of grass, which gives it a slightly sweet flavour. The flavour is great, and there is no aftertaste. You can't say the same thing about Smiroff - aftertaste is horrible.
There are many differences between different vodkas, maybe not as many as there are between the wines or the beers, but differences def. exist.