They don't really shrink. They simply move the goalpost. The unknown is infinite, so we can recursively explain something in terms of something else which is more fundamental, but we simply don't know where/when the rabbit hole ends. It's not that the discovery of quantum mechanics shrinked anything, on the contrary expanded it beyond our understanding.
So we are faced with 2 choices:
- we keep on playing this game forever. Effectively, we have explained nothing, but provisionally everything works due to theoretical models. We have tech, we have understanding and ability to interact with scales that are enough for human life and progress, everything is merry but we have _truly_ explained nothing. We don't know if the next "level down" will completely wrap around our understanding. And the next "level down" might as well be God, we won't know.
- we consciously pick an informed primitive. The "one free miracle" philosophers (and scientists) blabber about. Now, _if_ we can build a consistent model out of that assumption, _then_ we might have a chance to actually explain something. And there God is not really needed. Nature is obviously what nature is, why can't we accept that something simply is without being created? The very question betrays an entrapment in a space-time mentality where "there must be a before where nothing was, hence divine intervention" but we already know, form physics, that that is not the case.