The scary thing about the Bears is that a 5th round safety could be the best safety on the team, and yet still only play like a 5th round safety.
It's more of a league wide issue and less of a Bears specific one. How many teams have one good safety let alone 2? I think of my Eagles and I really like Malcolm Jenkins, but aside form that he'll be lining up with one of the following:
Earl Wolfe - Guy that can't stay healthy and has a hand full of starts in his rookie year to his name.
Chris Maragos - Career speicial teamer who's never started a game at safety.
Jaylen Watkins - Late round draft pick from last year who was asked to bulk up to compete at the spot.
Chris Prosinski - Who?
Ed Reynolds - Last year pick who never saw the field.
Going a bit further I think of the NFCE and there's really no safety better than Malcolm Jenkins, so that's an entire division. Thinking of the NFCN the Packers have a nice combo in Clinton-Dix and Morgan, but overall that's the exception, not the norm. Harrison Smith is okay, but far from great.
I just think safety is one of those positions where it's tough to get one guy, let alone two. The Pats won a Superbowl with McCourty and Chung. McCourty is very good, but Chung was cut by the Eagles while only being one season into a 3 year contract. He completely sucks in coverage, but in the right system can be hidden.
Overall I just don't think there's enough good safeties in the NFL for each team to be adequate in that position. It's sorta like QB, but for the defensive side of the ball.