Either the elephant in the room or the fact that the
Super Mario Maker games effectively killed the need of a new official 2D Mario game since talented fans can create better and more interesting 2D Mario levels than Nintendo devs themselves.
Enough about that, don't expect
Super Mario Bros. Wonder to be easy
as per Zippo (minor spoilers ahead). Expect this game to be a step up in terms of difficulty compared to previous recent Mario titles. I don't expect it to be Kaizo hard (at least not directly from Nintendo), but hard enough to punish casual gamers and/or give Mario veterans a worthy challenge.