And even the concept of one virtue being “better” than another
REQUIRES
an objective standard.
Exactly. If there is no supreme moral force in the universe then words like good, evil, right and wrong have absolutely no meaning. It all devolves to individual opinion. And if it makes me happy to rape you and then cut out your liver and eat it - who’s to say your opinion is more important than mine.
Bingo. You can’t even make a logical case for “right” or “wrong” without an objective standard, and the only objective standard that is sensible must come from an intelligence outside of humanity.
Plenty of atheists have tried to make such a case, but their arguments are easily deflated.