The biggest oversight is how small some of the kingdoms are compared to others.>Metro is by far the densest in the game>Beach and Sand are the Sparsest but also the largest>Those three were the focus of the marketing
It's easy to see why they've done it and such, and I genuinely enjoy the more Banjo Kazooie sized sandboxes of places like Cascade and even the Cap Kingdom, but the worlds that are padded out are so clear to see in their design>Luncheon surrounded by Lava Soup so you spend more time as a Podoboo than you do with Mario, even for the Boss>Spend a huge chunk of Bowser's Kingdom as a Pokio or whatever those birds are called. They're cute, but not what I want from Bowser's Kingdom>Bowser has a Samurai Kingdom for no reason (One thing I'd wish they'd kept from 3D world was the Neon aesthetic, I'd want a big carnival style area with possessing Neon Signs, Giant Robots and the like)>Boss Gauntlet in low gravity>Despite having Luncheon be a Lava world and just having Bowser's Kingdom, for some reason The Moon of all places is a lava world too
I love this game but people really do overlook some flaws in its design because it's a Mario game. The Secret areas similar to Sunshine that open up Post-game are the best parts of the game, I love platforming challenges like that.