They essentially did by trading for him one year after he was drafted by the Blues.
Cowen was not the only bad pick. Lazar and Bowers were low-upside picks, Thomson and Ceci have zero hockey IQ and Rundblad couldn't skate.
All of those were bad picks at the time. The scouting staff is not omnipotent and if they do something stupid with our picks they should get criticism and not blind faith.
I think it's a bit unfair to criticize picks of guys chosen around where the consensus has them ranked.
If Thomson disappoints (it's a bit early to be calling him a poor choice yet) then he's fair game, but all of Cowen, Ceci, Lazar, and Bowers were chosen where they were expected to go. The reality is not every pick is going to be made on upside, it's a balance of upside vs likelihood of making it that has to be made, and a team that always weights upside above all else runs the risk of finding itself lacking the depth to take advantage of the top talent they did find.
As for Runblad, his value exploded after we traded for him and the return we got when we decided to move on exceeded what can normally be expected out of a 16 OA selection. Tarasenko aside, we were better off with how things went than had we chosen any of the next 9 guys, and given our reluctance to draft russians at that time (be it because of the Melnyk factor or the threat of the KHL), there probably isn't a guy taken in the first that we realistically would have taken that would have been a better option.
Had we focused on upside, we could have ended up with Bjugstad, Jankowski, Shinkaruk, and Paarjarvi. All sorts of players can bust, some times it's development related, sometimes injury, but nobody has a crystal ball so if the guy is picked in the range where he should be expected to go, I have a hard time saying it's because of bad drafting.