Pure Reason. Where has it gone and why are people no following it?
To the shops, and because it runs too fast. 
Seriously, i think you need to be more specific.
I think Kant was replaced by Wittgenstein’s philosophy, and he was followed by Post-Modernism. It’s not nice to fool mother nature.
my real name,
neo-Scholastic
Because Kant demonstrated why Pure Reason could say nothing about the empirical world then Hume demonstrated why the empirical world renders all talk of Reason somewhat redundant.
Then you’ve got Wittgenstein and the official deconstructionists who demonstrated how even the rationalists had to resort to metaphors and metonyms and any number of other linguistic ploys because reason was not sufficient on its own to produce the results that they desired.
But you have got a few neo-Cartesians and neo-Platonists knocking around. They are still tolerated because they are such an amusing bunch, like watching drunks trying to play chess…
Pure reason still depends on perspective and even perfect reasoning can come up with an incorrect result under the right circumstances.
since this thread is located in Mundane Babble:
Pure Reason is located next to the Imitation Reason – which can be purchased for a fraction of the price and has a much longer shelf-life.
Here, have some.
Reason is a whore, surviving by simulation, versatility, and shamelessness. [size=75]–Cioran[/size]