It sucks for people who aren't able to get financial assistance from their family (I'm one of them) but this isn't nepotism. This is families doing what is necessary to get a first house in a lot of current housing markets. Nepotism would be if houses were only being sold to family members/acquaintances of the owners.
It's just a meme, since they're both highly anticipated movies with very different vibes releasing on the same day. I don't think most people are actually expecting them to compete (if anything, most of the jokes I see are about watching a Barbie/Oppenheimer double feature). It's the same as the Doom Eternal/Animal Crossing jokes a few years back