I'll get some flack for this, but I really couldn't care less about the environments in 2D Mario. Grass, Dessert, Ice, Beach/Forest, Lava. They've all blended together and at this point (unless we're talking about 64 or Odyssey) I don't care about the Mushroom Kingdom or its surrounding areas. Even the ghosts houses, generally very unique environments, have become bland and uninspired, using the same design since SMW. I would really like to see some variety in the worlds these games put out. They've made some short lived attempts, which I appreciate, and those end up being some of my favorite levels of the bunch. If and when Nintendo makes a 2D game that isn't Mario Maker, I really hope they try something new for the environments, and maybe even the gameplay, considering it's stayed mostly the same since the first New game.
Sorry about bashing on these games. I love them, I really do. I just want to get excited about their worlds again, the way I got excited about Odyssey's kingdoms.