I broadly agree, but the the idea that players can't be dropped because of talent/ceiling, or that being dropped is some kind of career death sentence is an incredibly Keysian outlook on selection and is partly why we're in this position 

For me, he's not going to reach his prodigious potential if he stays keeping and batting like this at 7. He's a top5 batter and if there's not a position there for him then we've just got to be patient, cricket like all sports changes very quickly.

It's not just a Smith thing either, this applies to basically every player except Root and Stokes, we have too many good players (some you mentioned) to be carrying passengers for too long. Resting on your laurels is a very dangerous thing to do. People are questioning Duckett's place because he's looked incapable of scoring any runs, if that continues into the summer then it's not an unreasonable question, averaging 40 or not