a reskin is either going to be differently colored than the original model unless its exactly the same color. and therefore will be more or less visible against certain backgrounds. maps are designed so that there are positions with high contrast and low contrast, which is one aspect of map knowledge. putting in differently colored models screws with this aspect of the game. also it will give an incentive for people who play certain positions on a map to pick a model that is harder to see against the background on that position.
overall it can only make the game worse, but valve doesnt give a fuck.
CS isnt the most insane in terms of graphics. however, the Source engine is a pile of trash. to be able to consistently hit people when i shoot at them, i have to play the game with multicore processing disabled, because Valves multithreading implementation in this 10+ years old engine is terrible and makes hitreg worse and adds input lag and renders a bunch of useless interpolated frames.
on 1 core, with my i5 4670K at 4.2GHz, i get great fps on old dust2, old cache, old nuke, old cobble, the maps as they were in 2015 2016 were fine. on updated versions, in some areas i drop to 130fps. if i turned on multicore processing, i would get up to 4x as much fps. but, these frames would still have at least as much input lag as if i was still playing on 1 core at 130fps. because the other cores are rendering their own frames independently.
they dont work together on 1 frame, and then on the next one, but they do 1 by themselves. so, the game doesnt respond any faster, it just artificially inflates the fps counter. it makes the game look slightly smoother, if the interpolation used to create data for the frames rendered by secondary cores correctly predicts what your enemies will do, which it usually doesnt.
for me, this game isnt playable unless i get at least 200fps on 1 core. preferably 240 because i have a 240hz monitor. those are my demands. valve could easily meet these demands. but they dont care about writing good software. they just want to take the easiest road to making more money.
when valve switches to source2, they will hopefully have a new multithreading implementation that actually splits the workload instead of having each core render a frame by itself. maybe then i will play cs again.