The colour of those bricks is a problem, at least for me.
It fucks up visibility, not in the sense that a player's model colour is hardly noticeable comparing to the walls, but because there are far too many colours of different brightness simultaneously in your screen.
Look at all the other competitive maps (apart from vertigo because it's a joke). They don't have so many colours of different brightness, mirage is pale red/sand, dust2 is sand and dark-ish grey which are pretty close when it comes to brightness, inferno is mostly gray-ish, they're not so colourful overall.
But you come to tuscan and you see yellow, orange, red-something and suddenly fucking light-grey, moreover - that light grey is divided into freaking "cells" (bricks), it would be OK for de_cobblestone because the whole map is like that, but tuscan is not grey and has never been, it's exactly yellow-orange.
I bet no one would like tuscan as a competitive map, and those cancerous bricks are one of the reasons why. They suck.