Just come across this issue when i tried to fire up L4D2 on my 2017 MBP with touch bar. Hit launch button in Steam, screen goes black, spinning beach ball, nothing. Hit escape and get the error message in a box on screen: Left4Dead requires texture compression but support was not detected. Im directed to some Windows c centric support pages. Ive contacted Steam support which was particularly unhelpful (boiled down to "Dunno, as on our disc assign boards") I noticed on the Steam discussion several people have had the same issue. Anyone got any ideas?