Nice to find this, as I was moderately underwhelmed by it, and can’t get my head around the level of praise it’s getting.
For the premise of Bowser marrying Peach, I actually prefer it over the same-old unexplained kidnapping of Peach. It made me think “I’ll accept a Peach kidnapping plot just one more time”. I suppose I’m just more accepting of some darker undertones, as long it’s from the villain, and possibly less aware of real-world forced marriage. But I respect your feelings, and am slightly surprised to not see others expressing this. I was surprised at first that they were doing this as it nearly confirms that Bowser’s interest in Peach is sexual (It may be political as well, but I don’t get the feeling that there’s nothing sexual behind it).
As for the gameplay; I also felt the level design wasn’t great. You seem to have a slightly different idea than I over how it could have been better. While you seem to want it to be more “open-world”, I was thinking that they went too far in that direction, though I suppose that there are some ways it’s not “open-world” enough. I think it’s just the wrong approach to how they blend the challenge-driven obstacle course style with the more open non-linear style.
For instance, Super Mario Sunshine is more linear from one perspective. Think Ricco Harbour; there’s a specific Shine Sprite that you can see high-up and you must get up there somehow. But you have to look at all the platforms available and figure out the best route to travel across them to reach the goal. In that sense, it’s actually better at challenging you to find your own solution.