I hate super mario world...and I think its the second worst 2D game in the series.
1: It's such a departure from SMb3(pure perfection, btw). The level design, the way items work in terms of when you get hit(why do i go from fire mario to small, only to be given a mushroom? I DON'T NEED A MUSHROOM TO GET BIG AGAIN).
2: Again, the level design. The themes are so different and all over the place. It's just weird, very weird. I personally adore the hell out of the standard mario tropes(it's overusage is what people hate, but don't blame SMB3 for that, blame nintendo milking the hell out of it). I'd take that over these tropes, frankly.
3: Yoshi. Ok, no, I'm not trolling...My first experience with yoshi was in Super Mario sunshine, and he was used for some of the WORST missions in that game...so that's where my biased, illogical opinion comes from. He's fine here and SMG2, but...I still hate him. Also, his platforming games are too easy imo and his story is even more basic than a typical mario games(I'm looking at whooly world)
So, yeah, screw Mario world.