I see a lot of worry about Miller, but I don't share that same worry. One of the signs I like to look at for projecting a player in the next season is how they performed down the stretch. Miller played at a 90 catch, 1200 yard pace for 5 weeks from the Rams to Packers games. It was a very similar stretch that Robinson had in 2018, minus the huge playoff game. For a wide receiver, I worry a lot more about a leg injury than a shoulder injury.
That being said, the Bears clearly need speed on offense. Denzel Mims is one of my draft crutches and combines a huge catch radius, body control and big time speed. I expect him gone by 43, but he's a run to the podium guy for me. But if the Bears want to hedge their bets against getting a big time speed guy, I wouldn't hate signing Demarcus Robinson, if they put a premium on knowing the offense with likely limited offseason work.
The Bears need a #2 in this offense, as Miller is the slot. Ridley is a good 4th guy who learned all the positions last year. Patterson is the wildcard. And honestly, if the Bears are able to pull off getting a true #2 WR, I'd make Wims available for a late round pick. I like him as a WR, but he's kinda redundant to what Robinson does, though obviously not nearly as good.