Fallacy: Arguing the person, not the argument, (amongst other fallacies). [In fact, you weren't even arguing anything, you just kinda made some base assertion that didn't argue against, let alone address, the actual argument in question].
Let's skip the weather and concentrate on the actual subject, (gods). You are seemingly claiming that everyone that is a theist, (believes god exists), has knowledge of that gods existence. If not, you're suggesting that people both believe in the existence of this entity, (ont), while saying "I don't know", (epi).
Nobody is asserting that anybody "knows", (epi) but that cannot be confused with (existence belief) (ont). If you contend - as you seemingly do - that (ont) and (epi) are in fact mutually exclusive, then I require something in the way of evidence.
Who has the onus? It is you my friend for a very basic and standard reason: We know that people can have a belief in something without knowing it to exist, (you'll concede this, stating that there are atheists that believe in things like multiverses without knowing whether multiverses exist or not). We also know that people can believe something doesn't exist without knowing whether it does or not. These are typical, observed facts of existence. You are suggesting something that is completely unobserved, (epi and ont being mutually exclusive positions), and hence you must establish that as being so.
Good luck btw.