Shaw has very likely been unlucky that all his terrible contact hasn't resulted in more of them falling in for hit. That said, he's still hitting badly.
Problem is there's nobody better to replace him with. I don't think it will do much of anything to demote him.
The Cubs lost several games last season based on the bad performances they got out of the 3B and catcher spots. If Shaw doesn't start hitting by the deadline they need to acquire someone, maybe even sooner They're at -0.5 WAR out of 3B this year.
You can leave a rookie out there struggling for a few months but at some point you've got to worry about winning. Brewers are on their heels, and the playoffs is no place for development. Jed's job is also on the line, I'd be more worried about getting in the playoffs if I were him.