It’s simple logic.
Take any part of the story of Noah commonly referenced by opponents: impossible to get all the animals in it, impossible to feed all the animals, impossible to create enough water to flood the whole planet, impossible to repopulate humanity with just Noah and his family—what am I forgetting to mention?
The logic goes like this: if God is truly the creator of the universe, then none of the above would be impossible or even difficult for him.
And if some other diety is the creator of the universe, then whatever creation story is attributed to them would not be impossible of difficult for them. Yet you have no problem dismissing those as “implausible”, and I assume you’d have no problem with scientists in general doing the same.