Sherfield, McKenzie and Roberts are nobodies as WRs. No one is saying Josh can make any receiver good. I no more expected him to make them into productive WRs than I'm expecting him to do that with guys like Hamler or Isabella.
As for Claypool, I'd say the only if is motivation. This is his last chance in the NFL after a successful start to his career but then seemingly getting too big of an ego too fast. And sure he'll have to show something in camp and preseason, but looking at the roster, I'm not sure he'll have to "shine" per se. I see them keeping 6 WRs but only see 3 locks: Coleman, Shakir and Samuel. Hollins is talked about as a locker room asset, but his ability is more PS, from where he can still influence the team. The only other guys to have shown anything in the NFL on the roster are him and MVS. Someone else is going to have to shine to make the roster.