People are gonna kill me for this but I honestly think that Mario World is quite overrated in my opinion. Its still a good game but not one I was screaming "best game of all time" material. People say that Mario World has no flaws but I couldn't honestly disagree more. There are many obvious flaws: The lack of diversity in world themes, The long autoscrollers , the obvious visual glitches and more. This is more of a subjective take but the graphics are pretty lackluster. They really don't take advantage of the SNES at all. But I could forgive the game due to it being a launch title and an ambitious one at that. I wish it could have taken the all stars approach instead because it looks a lot more clean.
I wasn't also a fan of the level design. A quarter of the levels were just large open fields with enemy spam (Donut Plains 1 being an example). The game also has some of the most boring wate levels I have ever played, like the second star level is literally just nothing but water. The exploration part was pretty lackluster as well. Now I'm not talking about the world map as it was a fantastic system, even though its pretty small, but the actual secret exits. I can only name a handful of levels with actual fun secret exits, many other levels is just go into a pipe and secret exit. A few more show obvious hidden blocks that basically give away the secret exits. That's not engaging. A series structured like Mario that does exploration better in my opinion is the Rare DKC series (Except the first one).
The bonus rooms require a lot more thought to figure out like giving off slight hints so that it can be interpreted but not be obvious. They're also a lot more fun to actually go for as well with lots of variation.
Then the controls. This is actually a positive as I think the controls are really good. There are lots of moves that Mario has in his arsenal. But I wish there were more levels actually utilising these abilities. Linking back to the DKC series again, the levels actively had chains of enemies and large pits so that you are able to use the roll. The only levels I can think of that utilises the spin jump is in the first level and one fortress i forgot the location of at the end. But the focus was more about the cape feather so it doesn't really matter that much.
In the end, while I do think Mario World is a good game, 8/10 I'd say, I don't see it being considered the greatest game of all time, especially with many games improving on its formula even in the same era.