And even more people believe there's an old man on a cloud judging everyone, so what?
Burden of proof is on the person making the assertion in both cases, but we can’t prove without a doubt that god doesn’t exist even if we don’t feel there’s enough evidence to suggest he is. There is, however, concrete evidence the earth isn’t flat, so no matter who the burden is on it’s demonstrably false.
Put another way: You can concretely observe without a doubt that not only is the earth not flat, but also that it can’t be flat. We can’t confidently say god can’t exist.
(a) "I can prove earth is not flat" (using this methodology) (b) I cannot prove there is no God, though I may believe the prevalence of evidence does not support the hypothesis, there's no scientific test that I can design.
I can disprove that the Earth is flat with the incredibly varied, concrete, observable evidence that it is not. It comes in many forms and is undeniable, hence the lengths flat earthers have to go to to “prove” the evidence is all just a collection of lies that serve some nebulous, nefarious purpose (they don’t even agree on what that is) that serves some faceless evil group they prop up (usually “the deep state” or Jewish people). On the other hand, I do not have concrete, observable evidence that God does not exist. That’s the thrust of my point.
This is essentially Descartes evil demon issue. If you can't disprove that an evil demon (with god-level powers) is deceiving you at everything you perceive, then how are you going to be sure about anything? (including that the Earth is not flat?)
It has always been a difficult philosophical issue about how much we can trust reality itself.