Which requires you to believe in God first. And if you sincerely believe in God first, then there's no need to have supernatural evidence because you already believe.
And if supernatural understanding must be granted by God, then you can't blame people who haven't been granted this understanding for not believing because - they haven't been granted the supernatural understanding!
In the end, if you must believe in God in order to receive an understanding of how he exists, then you don't really need that understanding to begin with - which begs the question as to why you bring up supernatural proofs in the first place when debating the existence of God. If nonbelievers don't have access to these proofs, there's literally zero reason to bring them up with the expectations that you're arguments about the supernatural will be accepted.
Except we can open the hood of the car and view the engine. We can study how the engine works. But let's work on this analogy.
If a person who has never seen a car before saw one move, he might believe it moved by magic. If you explained to him "The care moves because an engine powers it, a contraption that eats oil," he might not believe you until you show it to him first. If you don't show him the engine or you don't have the means to showing him the engine, then there's absolutely no reason why he should believe the engine moves the car just because you told him to. Now, he may trust what you say because you apparently know more about the car than he does - which is okay too, but that doesn't mean the person who is skeptical is any less wise.
What if we're in a similar situation and I tell this person the car runs off of magic, and he believes I'm lying? Would you then call him unwise to doubt me? If both the person who claims the car runs off an engine and the person who claims the car runs off magic refuses to open the hood - why would you criticize the unknowing man for not believing either of them?
So if the supernatual exists, you can't criticize people for being skeptical - especially if you claim the only way to understand the supernatural is for God to pop open the hood of the car and show you.