Calls for an "immediate impact" at CB through the draft. Do they make sense?

If a rookie db will be drafted high he will have all the opportunity to start. It is a difference in being a starter and earning the position and being an impact. Most are brought on slow. CB has been a position in most cases where they don't come out like gangbusters,but to start as a nickel at best an work your way into that role can happen. I just want the best players on the field which hasn't always been the case at times in our secondary.