As long as theists keep asserting that everything must have a creator due to some version of the Cosmological argument, it's a perfectly valid question. Either everything needs a creator, period, or we accept that something outside of the universe may exist without a creator.

One of the reasons some people take the idea of a God to be reasonable is due to the issue of complexity which tends to beg the question as to how such occurred. However, the idea of a God also begs the question of complexity, which I took seriously. P1: God is denoted as at least a non-contingent intelligence/mind. P2: Cognitive capacities are processes and thus contingent. C1: God is denoted as at least non-contingent contingent. C2: God is incoherent, thus impossible, thus non-existent. This argument serves to point out that the claim of a God is an assertion that is in conflict with what we actually know such that it is at best a fiction and at worse a falsehood. I grant that one can claim that "there could be an intelligence/mind that is non-contingent" , but I could never grant such a notion given what is known such that such a claim REQUIRES substantiation. We know intelligence/minds are extremely complex things. I will grant that this type of an argument may not have been made in the far distant past, but now, given our development of artificial minds, brain organelles, understanding of the brain, and more - it is not something that should escape anyone's notice. I will also grant that my argument will not rescue some from a belief in fiction, since, there is no end to the parade of fiction that one can make up in an attempt to save an idea from being fictional. The Monty Python's Dead Parrot Skit made this abundantly clear decades ago.

It's not necessarily the best argument against any one religion in particular, but it's a perfectly valid response to the kalaam cosmological argument. Theists will always say that it's not special pleading because God is the uncaused causer, but that just presupposes God and sidesteps the question. If the Universe is so complex and finely tuned that it necessitates a creator, an infinitely more complex creator deity would also necessitate a creator. Kierkegaard is pretty based tho

If god doesn’t need a creator neither does the universe is a really simple concept Until a god can be proven it’s not a logical answer We don’t know if the universe has a beginning we do know about when it started to expand but not begin

When atheists ask “who created God?” they aren’t actually making any argument. It’s just a response to theists arguing that “the creation requires a creator”. So to demonstrate how that’s not a proper argument or statement, they ask you the same question.