Quest over!
I think another weakness of so many sidekicks is that it prevents any one supporting character from really getting their due. You could have a movie whether the central dynamic is:
- Indy and his shifty, British WWII pal
- Indy and Marion reunited (the Darabont draft)
- Indy and his old mentor turned Ben Gunn
- Indy and the greaser kid whose mom's been kidnapped
But instead of doing one or two of those and giving them enough attention, it does all of them poorly. Ray Winstone is given nothing substantial to after his treacherous turn in the prologue; Marion is given nothing substantial to do after a fun reveal (one dependent on shrouding her identity in a contrived, pointless way); Mutt stops being interesting once the court-mandated reveal that he's Indy's son occurs; John Hurt is just used as a device that turn problems Indy should be solving himself into foregone conclusions. In my opinion, it was a huge waste not to make Indy himself a gradual victim of the skull's power -- Nur-Ab-Sal style -- as it might have created some sense of jeopardy, or, say, a third act motor of any kind, both of which the movie lack.
It's utterly baffling.