Osborn and Bourne are solid possession receivers, nothing amazing but consistent good players. Randy Moss didn't do crap on the Raiders, Stephon Gilmore had a bad PFF player grade on Buffalo. It's a team sport, players don't perform in a vacuum, they need the team to be good. On a better team players like Bourne and Osborn contribute. It's not surprising that Jonnu and Agholor left Mac Jones and went back to being productive role players.
WR's are the last thing a team on the rise should add, because if you can't do the other stuff correctly (blocking, scheming, running, passing) diva WR's are going to make a stink and become a locker room cancer.