You understand this isn't real, right?
The Wall would never have stopped the NK. The Wall couldn't possibly stop the NK. From scene 1 of episode 1 or page 1 of book 1 the NK was 100% sure to make it past the Wall because that's what every single second of this has been leading to. They could have included a magic artifact that vaporized ice. The NK's touch of Bran could dispel the wards. The sea could freeze so that the dead could walk around it or they could have written 1000 other ways to do it into the story. They used the dragon method because the show is turning into Michael Bay does fantasy. The showrunners are way too in love with their special effects and have no interest in a coherent storyline.
From the very first second they showed the dragons in battle it was completely clear that they were overpowered and needed to be nerfed,. If Dany had three and nobody else had any there was no endgame story. The NK could have had a billion wights and Cersei could have hired every mercenary alive and Dany would still win easily. The NK getting a dragon WAS NOT about giving him a way to bypass the Wall, it was about giving him a weapon to use in the end game because otherwise the armies of the dead had no chance.
The show has never ever shown that the NK had anything that would allow him to break the wall easily. People say he could freeze the water, but we saw in the Hardhome episode that he didn't pursue them, why wouldn't he do that if he could freeze the water?
I'm not opposed to the NK getting a dragon, I'm opposed to the way he got it and how the show makes it seem like he wouldn't have any means to break the wall otherwise, other than his army fighting their way through it.
If the writers wanted to show how overpowered the dragons are, they did a bad job. Night King almost got a second dragon with his auto aim and it looks like Daenerys didn't even get a third of his army.
IIRC, in the books, the Wall is said to be enchanted by magic, and they've never said that breaking the magic means the Wall will fall down. The closest we've gotten reading about how the magic works IIRC is that Jon doesn't feel the connection with Ghost when they're on the different sides, and that Coldhands says he can't pass. On the other hand, the wights in book 1 and season 1 were able to revive on the other side and went after the Lord Commander. Also, in the book, we haven't read about the Others' actual leader yet.
However the books will handle the Wall being breached or falling down, whether be it the horn of Joramun or something else, I'm damn sure it'll make alot more sense than in the show.