Yoshi's Island is a stage that's from the not-Mario game Super Mario World, which is a Yoshi game where you play as Mario but is not a Mario game because it has the egg icon so ignore the Mario music that plays pls thx.
This stage is half walk-off, half not. Though the pipes on the not walk off side make recovery difficult. Also, those yellow blocks spin around when attacked so try not to get in the hole in the center. Competitives dislike this stage because it is a walk off and returned over Yoshi's Story despite this stage representing a much more popular and iconic game.