Porygon Was Innocent: An epileptic perspective on the infamous Pokémon episode

The NES Classic is somehow able to detect rapidly flashing screens in its built-in games and temporally blur them as an anti-seizure measure. Nintendo certainly learned its lesson from the Pokémon incident.

That's a better solution than putting warnings in front of every game.

The cookie banners of the 90s

Probably easier to implement in the NES case too: toggling the screen background color rapidly was a common trick used by NES developers to represent large explosions and the like. That would be easy to sniff for and blur out with few detrimental effects.

Doing the same with today's visually intense games, like Rez and Tetris Effect, would be more difficult. The potentially harmful visual effects are more subtle than simply rapidly flashing the entire screen background, would require heavy processing to scan for, and if you filtered them you risk compromising the visuals that some people purchased the game for.

Best to just warn them so photosensitive people know what they're getting into.

Modern games can just not include them!

Cookie banners aren't warnings though, nor legal requirements; the legal requirement is that the user has to make an informed choice before the website is allowed to place tracking cookies. It was the websites themselves that implemented it in a hostile fashion to intentionally annoy the user into just accepting it or to complain to the EU. But the EU never mandated the big cookie banners / popups. Be very careful with who you think has caused that.