Thing about TE is that it's not always about their skills, it's about the QB, the O coord and the gameplan. So to say a guy has arrived and another guy hasn't doesn't seem all that useful.
Clark and anybody else can't catch what isn't thrown to them. Face it, on 15-20 NFL teams, the TE is often no more than an extra blocker who catches 2 passes a game.
As for Clark, the fact that there are plays designed for him to catch the ball 20+ yards downfield when they have Wayne, Harrison and Stokley to go to ahead of him says something about his ability IMO. Is he ever gonna be as effective as Gonzo having to be played as a 3rd WR by some teams? probably not. But definitley a top 10 TE (at least) in the near future.