Trying to upgrade goaltending at the deadline almost always fails anyway. It's such a mentally focused position, that changing of teams, systems, environments tends to throw deadline acquisition goaltenders for a loop. You can maybe upgrade your backup goaltender and have them step in if necessary, but by that late point in the season...you're kinda stuck running what you brung as far as starters go.
I think the Blues learned that lesson back when they tried to bring in Ryan Miller mid-stream and it went absolutely atrociously. Not that he wasn't still a quality goaltender at the time, but he just never seemed to get comfortable. That seems the be the way it often goes. For goaltenders, even more so typical deadline pickups that can integrate more quickly.