I think the habit of attaching “agnostic” to ideas about existence, when precisely no evidence is forthcoming, must cease. Isn’t agnosticism concerned only with the quality of one’s knowledge, after all?
Come to think of it, words like skeptic, doubter, atheist, or just saying, “I’m quite sure that’s not true“, all contain the idea of expressing a demand for better evidence, that is, if any evidence supporting some cult claim is to be had. I cannot be agnostic about any of the thousands of gods — from Wotan to Allah to Elohim to Nezhataizi — when the boundaries of knowledge have never been established for any of them!
I cannot know about many things in the world, least of all being the many and oft repeated claims made by priests, rabbis, imams, spoon-benders, street hustlers, and other tellers of tales and sellers of products. I would not be so quick to take the position of agnosticism with regard to my knowledge of their claims! I may be able to afford to be agnostic about some aspect of a well-defined problem; any claim with no boundaries must of necessity be rejected outright.