In that case atheists should have to argue against my version of God. I define God as the Empire State Building. Surely that is the most reasonable version of God since lots of people see it every day, there are tons of pictures and videos of it. We have historical documents showing when it was built and how. The Empire State Building definitely exists. I would say that my God is the most likely to exist out of all the theologists Gods except that some theologists have defined God in even more inane ways. If God is merely "existence" then the likelihood there is a God is very very high. Indeed, in that case, saying "There is a God" is likely performatively redundant.

So yes atheists have to respond to the best arguments in favor of the existence of God-- but only so long as the God being debated is a) not tautologous and b) somewhat similar to the God most people believe in. Even given all the religions there are still striking commonalities between them... until one gets to the theologists. I actually have nothing against theologists. I think that flexibility in their understanding of God (particularly of the theological non-realists) can lead to really inventive and insightful ideas about humanity's relation to itself and the universe. But I'd rather not pretend what they say has much of any relation to the beliefs of real practitioners.

Btw, your view of what God is is still on the radical end of theologists. If a Catholic priest published your view, for example, he'd be excommunicated. If an evangelical said it he'd lose his church members and if an Imam said it there'd be a fatwa.