Answer:
4. I think. But I'm not an artist.
Explanation:
I'm not an artist of any kind, but I've always liked this painting. I've never thought about why until you posted this question.
It isn't because of the indoor setting. Impressionists can and do paint many things that are indoors.
The figures are not formless. Those girls are very beautiful.
Many figures (including the central male) don't have shadows, or none that I can see.
It's the asymmetrical composition I think. If you drew a line in the middle going up and down, almost all of the figures would be on your left. Yet the man (who really is at the center of your vision) emphasizes the beauty of what is in front of him.
