You can't have it both ways. You can't say that Jon killing the Night King was not hinted at, while Arya's was. That's certainly not the case. If anyone was hinted at killing the Night King, it was Jon. Not Arya. Arya's story had nothing to do with the Night King up til now. Absolutely nothing.
It didn't work at all. It wasn't an emotional roller coaster. It was an empty shock moment, that had absolutely no emotional resonance.
Arya killing the White Walkers doesn't add anything to the story. If Clegane had killed the Night King, the white walkers would still be dead, they'd still be done weakening Jon. Arya killing him doesn't add anything uniquely to the story. There's no emotional weight there. It's the same as any random character doing it. Jorah could have killed the NK, and it would have been just as emotionally satisfying, just as narratively consistent.
But if Jon had done it, you would have had a significant moment for him. It would have been a resolution of his main obstacle. As it is, it'll never be resolved. He's not the Prince who was promised. He's just some random guy. And now his purpose is to be King... which he never wanted... ? Cool. So satisfying.
The writers decided that subverting expectations was most important. That's why they had Arya do it. It adds absolutely nothing to the story other than shock value.
Sure you can have it both ways lol. Melisandre said Arya will close blue eyes forever in other words kill someone with blue eyes. No one said specifically that Jon will kill someone with blue eyes forever, if so and Arya kills the night king then sure then I'd call bull****. 3 stare downs is not as strong of a hint my friend lol. We thought it was though understandably. The set up is there in season 3. They didn't care about emotional resonance with the ice zombies lol except kill the night king before they kill us all. It was prince or princess not just prince.