stream of thoughts:

"all countries" doesn't really show all countries. It seems all countries might be in the pool, but there is no weighted randomness, so you end up getting the same flags, and only a few new ones.

Forcing all flags to be in the same aspect ratio really makes the flags look strange, or rather, not how they really are. This also makes things like Monaco/Indonesia identification more difficult, and flags with horizontal stripes to look strange (Sudan, Cuba, etc).

Some flags seem to look odd or broken? Such as Ecuador which looks like a kid drew it and is pretty broken. Some flags have a weird border around them too, as if they haven't been placed or rendered correctly.

I'm not sure if having a list of flags just below the quiz helps the integrity of it. I'm also not sure of all the AI generated stuff. Are people really mixing up Morroco and Veitnam? Getting to that page again is difficult and unclear, you need to click the flag from the country page, or get it wrong in a quiz. I feel it's a little confusing to have separate pages describing the country and flag. Especially considering its a website about flags.