Anything that's judged, rather than measured.
Thinking about this a bit more, I'd also make another blanket ban on team sports.
To me, the Olympics is about individual excellence. It doesn't seem right that someone like the Argentinian goalkeeper Oscar Ustari can win a gold just because he happens to play in the same team as Messi, Angel Di Maria, Zabaleta, Mascherano, etc.
He's had only 336 professional appearances in his entire career, and only played with the full International squad twice. Contrast with Jordan Pickford who has had over 400 appearances and he's 8 years younger than Ustari. They're both still playing.
I'm not trying to say Ustari is a
bad player. tbh, I don't know anything about him, and didn't know who he was until I looked up some stats for this post, which considering he plays the most popular sport in the world, and won a gold medal doing it, I think says a lot.
He's [probably] not a brilliant goalkeeper, nevermind a brilliant footballer. He's been signed by mediocre teams, such as Sunderland and Getafe, and didn't even get a game for Sunderland. At the time, Pickford also couldn't get a game for Sunderland and was loaned out.
Compare Ustari with someone like Zlatan Ibrahimović. He was not the best footballer in the world, but he was individually brilliant, and to me, is much more in line with what I think being an Olympian should be. Playing for Sweden, there was never much chance of them winning a gold, just because the rest of the team were not that good. It didn't matter how good he was, he could, and would, miss out on a medal due to other people
who were supposed to help him, not being good enough.
Even worse than all of this, IMO, is that if you have played in the World Cup, and you're from a European national, you're not allowed to compete in the Olympics for football. So, some of the world's best players are by default excluded, so what are you celebrating?