For QB specifically, I have this view that the team basically understands that this team won't be overly competitive without Lamar if he misses extended time. And I'm kind of fine with that.
I think most if not all of the decent backups in this league are still going to cost you several million $ a year as a backup. The Flacco's, Dalton's, even Drew Lock's of the world are getting $3-6M a year as backups. I just don't see us committing that kind of cap space to a backup at this point, especially when pretty much none of them would run the offense the way Lamar does.
I'm not opposed to draft picks either, but obviously you're pretty much never taking somebody earlier than round 5, and realistically, like rounds 6-7 or UDFAs. Which means there's pretty much no shot they're ready to play in year 1 and its a total dart throw if they'll ever even be a backup-caliber in the league.
So for me its not even like a worthy discussion point. They take a 6th rounder to compete with Johnson, cool. If they roll with Johnson, same cool. I don't think it matters. If they have or had serious fears about Lamar's availability, they'd need to pony up in the FA market to get a veteran who can not sink the ship if Lamar misses a month.