I think it's interesting how similar Arthur and Merlin’s character flaws are.
Both of their first attempts to win Red Shoes’ love are disingenuous: Merlin tries to use a love spell while Arthur pretends to be dying so he can get a pity kiss.
They're both superficial but in different ways.
(Yeah, all of the F7 are at least a little bit superficial, otherwise they wouldn’t have gotten cursed but they have it the worst imo)
Merlin prioritized looks over everything else. It’s his entire character arc in the film. He constantly makes comments about appearances, his included. His first appearance post-prologue is him complaining about how they look, when snow/red shoes calls them awesome he immediately brings up their appearances, he makes comments about King White, and he does it so often that Red Shoes even points it out. Merlin’s arc throughout the film is him realizing that appearance isn’t everything and that a person's value comes from what’s on the inside.
Arthur, on the other hand, focuses on how others perceive him rather than looks specifically. He brings attention to his name being on the lease, trying to make himself look better, when they’re all living there on Jack’s dime. He doesn’t care about being worthy of Excalibur as long as others think he is. He wants Red Shoes to see him as her hero, but he doesn’t help Snow White when she’s in distress.
I headcannon that he view himself as the F7’s leader, or at least he wants to be. He’s Arthur Pendragon, so in his mind, he should be the leader. I also think Arthur expected to be the first one to break the curse. Don’t get me wrong, I do think he’s genuinely happy for Snow and Merlin, but I also think he’s slightly salty that he wasn’t first.
Arthur wants to be a legendary hero, but doesn’t understand that no legendary hero sets out to become one, they just happen to become one on the way.
It’s hard for me to put into words, but he kind of reminds me of Gaston from Beauty and the beast without the malice. Likewise, I think Arthur meeting someone like the Beast would be a great catalyst for his own character arc: someone who’s good at heart, but due to their appearance, is shunned and harassed.
Red Riding Hood from the credits is a perfect example. Based on her reaction when she transforms, she’s clearly been mistreated due to her lycanthropy. In a traditional fairytale, she would be the monster that Arthur would need to defeat. But this isn’t a fairy tale and she's not a dangerous monster. She’s a person trying to live her life and if Arthur wants to be with her, he needs to step away from the title of a legendary hero and reevaluate who he actually wants to be.
If Arthur truly wants to be worthy of Excalibur, he needs to stop being a hero for just pretty princesses in distress and become a hero for everyone: royalty, peasant, human, or otherwise.