This is a ridiculous criticism. Ancient Greeks didn’t look at sculptures of ripped dudes and “feel bad about themselves.” They got INSPIRED and felt GOOD about themselves. Be like an Ancient Greek.
His biceps and thighs are well within human proportions I see daily in regular men.
In fact, the least likely portion of him would be the modest endowment, something that a modern man would almost certainly not admit to.
Apparently Michelangelo knew it was missing, because it's due to a flaw in the marble.
I think individually the proportions aren't crazy, but taken together I think they contradict eachother.
For one... seeing David in rare moments (you listed this example down below, but it was not ancient nor greek) or any art is very different than the current effects of advertising. In those cases, between long stretches of real life, it’s possible or even easy to appreciate. When bombarded constantly with an unrealistic ideal hundreds of times a day, it has a different effect.
What’s next, protesting the Venus of Willendorf for being too thicc? “Unrealistic image ideals” have millions of historical precedents. They are fertility symbols and they can serve to inspire if only you choose to be inspired! Choose to be inspired. :)