I’ve never heard it put quite this way, and I know that it is implied within numerous arguments for atheism, but I think, by just making it explicitly present to consciousness, that this is a pretty good reason to doubt God’s existence:
We might have found, over the past two centuries, that the universe is very, very large, but also quite young (as in Bishop Usher’s 4004 BC young). Likewise, we might have found that the universe is spectacularly old—as in the current figure of 13.7 billion years old—but also quite small (confined to our solar system and mostly just the visible stars). In other words, if, over the past two centuries, science had in fact discovered that we live in a very old universe that is very small, or a very young universe that is very large, these discoveries would have been very bad news for atheism (for neither situation provides either enough space or enough time for mere chance to select Earth as one of the lucky planets with life on it and then build that life to its current levels of diversity and complexity).
But, in fact, here we are with precisely the type of Goldilocks mix of just the right conditions for the thesis of atheism to work. Now, of course, it is true that there are aspects of the universe (such as the cosmological constants and the complexities of the first cell) that might well suggest that, even with all the time and space that we do have, it’s still not enough to account (by chance) for what we’ve got. Atheists have a retort that gets them more space and time (the multiverse), but my point is that atheism might have been in even worse shape on such matters if the universe had been found to be either very young or very small.
But it wasn’t, so score one for the atheist thesis.