It’s possible he’s freaking out and forgets he has the Force in his encounter with the Rancor. I know canon says Rancors are not native to Tatooine, but I used to imagine he’s facing his greatest fear, the monster he used to hear echoing across the desert. Now he’s trapped in a room with it, and for a moment forgets everything he’s learned.
However, I feel that it would be worthwhile for this edit to attempt to make Luke throw the skull or hit the button with the Force.
If we assume that he freaked out and forgot he has Jedi powers this only makes stronger what Yoda said in ESB (he’s not ready). And I believe what you said is correct, Luke doesn’t act like a fully trained Jedi sometimes. I hope something can be done to improve his behaviour as a Jedi.