If their overall cosmetic item desirability weren’t so low, then their crates would sell much better.
As it is, I’m pretty sure that only a tiny handful of the cosmetic items are “take my money” to most players. What’s worse is that cosmetic items are not manually disenchantable, so getting unwanted cosmetic items pretty much feels like doodoo. There is just too much worthless fluff in those things.
At this point, I would say tweak the crates so they contain fewer “almost certainly worthless to most players” cosmetic items (most profile icons, generic emotes, generic cardbacks, etc.) and more Prismatic cards. It’s important to make much fewer crates feel like total losses to sell 'em keys seriously.
As far as free keys go:
DO NOT INTRODUCE THEM UNTIL CRATE DESIRABILITY IS FIXED ERRING COPIOUSLY ON THE SIDE OF TOO MUCH VALUE.
The introduction of new free keys is their second chance to give the players a good sample experience with crates in order to sell some o’ 'em keys. If they botch this one, too, then they may as well chuck their revenue people into the Sea of Judgement. =S