I have to agree that this moment s a bit too vague for a first time watcher without background knowledge.

Since the movie has already established visions for Rey, maybe a short, flashy vision of the Death Star Throne Room could be inserted when Rey stands on the shore, preferably intercut with closeups on the dagger.

Maybe you could go even further: Show a vision of the Throne Room from RotJ when sje first picks up the dagger and then one from the present as she stands on the shore. The closer she gets physically, the closer the visions come to the present. That could be kinda neat.

And another idea: Maybe 3POs dialogue could be changed in a way that he explains (after his wipe) that the dagger has an inscription that also says something to the likes of “To the sworn guardian of the wayfinder”. This would imply that the reason it is leading to the wayfinder is so the guardian can track it down should it be stolen.