I left Spruce out because he was a FA and your post was titled '2016 draft a bust?' so I thought you were talking about only the picks. In any case he's in the same boat as the late round WR picks. The best of the WRs in any draft typically take a while to develop; personally I would think a 4th or 6th round pick (or a UDFA) would take even longer ... and have only a slim chance on average to ever amount to anything.
Maybe we as Rams fans have been spoiled by the success of previous Rams drafts where we have seen unusual success from some of their late round picks so now we have come to expect it?
I love Deacon Jones and wear his white #75 when I go to Rams games. But wouldn't you agree that he is the exception rather than the standard for late round picks?
AlbaNY_Ram