Chairmansteve didn’t ask about theoretical paintings of watermelons that you have imagined though, he asked about Water Lilies by Monet, which is art that famously exists and is liked by many, many real people.
If your point is “all art is propaganda aside from art that exists and must be replaced piece-by-piece with hypothetical counterparts in my head to support this conjecture” you could have just written that. Though “some art is propaganda and some is not” is less profound sounding than “all art is propaganda”
It could be merely that watermelons are beautiful. Or it could be that the artist supports the people of Palestine.
For a less extreme example, think about the paintings of Norman Rockwell. Are they just pretty images? Or do they communicate norms?
Think also about what is censored vs what is not censored.