I understand your point- I've downloaded CS:GO mod packs a few times myself. They ruin your FPS and look terrible. I was also looking for a "clean" vanilla build like the ones in computer clubs in the 2000s. I finally found the
classic CS 1.6 client on the CSGet website. It's a completely original build with standard weapon and player models, default sounds, and no ads or hard-coded auto-connects. The config file is fully protected against overwriting, so shady servers won't be able to alter your menu or flood your console with spam. I’ve been playing on it for a month now and have no complaints. Do you enjoy playing on classic maps like de_dust2 and de_inferno?