It was a mistake for Sakurai's wife to design the menus for his games. They all look horrible.
It was the same style they used in Brawl, except worse because shit in Smash 4 is way less logically placed. And the style isn't unique either, the general aesthetic also is similar to Kid Icarus Uprising.
I don't want to insult Sakurai's wife or anything, but she needs some inspiration to be able to make a new UI from the ground up. It looks like she really enjoyed the Brawl UI and just keeps using it over and over.
Smash 4's horrible implementation is truly understated. All the single-player content is inexplicably hidden behind "Games and More" with the same visual emphasis given to Smash Tour, a single mode. Smash Tour is given main-screen privileges for no reason other than "this is a new mode for this game".
"Games and More" doesn't tell me anything. What the hell does that mean. "Game?" I'm already playing a game. "& More" is even more vague. The truth of the matter is, everything got bunched together in this section and they couldn't come up with a name to describe it all, so they just with generic whatevers. They could've just called it "random shit" and it would've been more informative. The fact that they didn't know what to name this category makes it abundantly clear that they needed a better hierarchy.
Smash 64 and Melee have the best general idea. Things are divided between multiplayer and single player. Then you have trophies, options, and Statistics. Within single player you can have the Single Player Events, Classic, All-Star, Master and Crazy Orders, etc. (not necessarily in that order). Within multiplayer you can have 2-player Events, special Smash, "Straight up Smash", Online, Smash Tour, etc. (again, not necessarily in that order). Within Data you can have statistics, Challenges, Video Replays, Stage Creator, Masterpieces, etc. Within Trophies you can have Trophy Rush, shop, Gallery, Hoard, etc. Far more logical, far less bizarre hierarchies.