What defines a world?

I don't really have a lot of experience with building worlds, but something i'd imagine helping would be figuring out what makes earth earth, and then diverging from that. For example, something that makes earth earth are laws of nature and science. Not what if there was a world where those were fundamentally different? Or didn't exist at all? What would have to be cultural changes/the conditions for life to still exist?
Or something else that makes earth earth are the rules and morals people have and follow. Switching up core aspects of those could also work. For example, creating a world where there was no concept of fair or unfair. Or a world where there is a completely different idea of what love is. Changing up the core things that make this world what it is might help in creating worlds that feel more varied.
Of course, i have no idea if that isnt what you've already done, but yeah, that's what i would do. Find all the things that make earth earth, and then take them away until something different comes to life.
And honestly, if some things are similar to earth, thats fine. Because this is what we know and can relate to, so having some similarities will always make us, your audience, feel a bit more at home in the worlds you create :)

Oh and one more thing i thought of, maybe thinking about the point of your world could also be helpful. Like, does exist purely to make a perfect battleground or maybe as a thing of beauty? Or is it supposed to teach a lesson about something specific, for example how narnia was created to make stories about God more accessible to kids and adults? Figuring out what the point you want to make with the world you've created is supposed to be makes it easier to focus on what is relevant to that world, and what things you can change at will because they dont really matter…