I feel the opposite on that matter regarding world, it's good that it is not set in stone with mobius and stuff, cause that would limit the creativity of the games, one game you can have a world full of humans and looking grounded enough like Unleashed. another game be like colors where it is more fantastical and alien, a third game can have Angel Island, and then you can go to other worlds like storybook games, you can then travel from Island to Island like Rush Adventure and so on. Sure the games are inconstant in quality and tone but i don't find the world to be a real problem as long as they are doing good with it and retain some familiar locations like Green Hill Zone and stuff -as much as that zone is overused those days- , it's not like Mario have some named world to my knowledge, and that allow any game to be set anywhere and do anything without it being tied to previous games, in fact the weaker games are those that are directly in the same world like New Super Mario Bros series. A better example is Zelda, sure games are set in "Hyrule", but they are so so different in tone and style they may as well be set in different universes, yet that don't affect the quality, in fact that's part of the charm of the series. Sure we have traumatic experiences with Boom stuff and the upcoming movie that all they do is fragment the image of the franchise, but i don't necessarily blame the world, but the overall direction of them.