You still make inferences, they just have to be more… carefully placed, I suppose. In particular, things that are relatively unchanging that were made as a sort of a steeple to the game would be things to theorize about, such as the contents of her room in the real world, or the type of Nexus she goes to, or maybe even some of the endings. (I'd still personally like to know what's said in the opening sequence that plays when you start a new game.) Her dream world, however, is more or less just an art gallery of several different authors to the game, and it seems pretty obvious that they didn't have any one concept in mind while making the game, just a kind of "this would be an interesting area let's do that" and then they put it in the game. It may disappoint some people, but there's really not some great canon explanation that can be unearthed like with other games.
It's less orthodox theory making than the other fangames, but 2kki is generally less orthodox of a fangame all together, since it's such an open ended collaboration project. People can stop making content for the game before they're even done, but it can literally just be woven into the fabric of the game without a hitch, and people won't even be sure whether it was finished or not. The creators aren't trying to convey such a specific story as people like to theorize about, because they're legitimately unable to. If you want to pick out a few specific aspects of the dream world that entertain you and make inferences about them and only them, then go right ahead. But just be aware that it won't be much more than a story you've created entirely on your own since it leaves so much else out, assuming that the point of theorizing is to figure out what the author had in mind.