Lore balls trumping game play. Karn is a colourless dude.
It does feel a bit white in its effects. Of course, White is only allowed to be garbage since they stopped it nerfing anything, so he can't be white. Small outclassed dudes and basic o ring effects is all white has left. Without nerf effects like stony silence and before that global removal like balance or cataclysm white serves no purpose. Piddling taxes is all white gets. All of white's functions bar pathetic hatebears and splashy unplayable angels go against what the data says people like. So we have an entire colour neutered because some tossers at wotc can't understand what the data does not tell us, that people like balanced games and don't always want what is best for them nor sometimes even know what they want, only what they think they want. This is why we ended up a few years ago with Stoddard telling us how cool Emmy, Promised and was when it was being energised out with no answers. White is an answer colour, a lock colour, and previously a global land kill colour, a tax colour, and a 'no' colour. Such things are not de rigeur.