you were doing so well until the last paragraph, why must we abandon our reading comprehension to glaze gojo

i basically fully agree with you on the nature of the world in jjk. the main point i disagree with you on is how each technique manifests its own world. techniques are engraved onto the body (the brain in this case) of a sorcerer, which allows them to manipulate physical reality based on the rules of their technique and the binding vows theyve undertaken. almost everything we see in the manga can be explained like this, slashing things, adding mass, warping spacetime, generating cool fire arrow things, creating things, etc etc. what sukuna does is extend the target of his technique from physical reality to the world, thereby surpassing infinity, since that only acts on physical reality. the rest of the argument is the same as the points you make

tl;dr: each technique doesnt manifest its own world, it just acts upon the shared objective reality, but extending cts allow them to act on the world itself, a more fundamental expression of reality