Nintendo started doing DLCs after 2017. Which again makes me wonder if they're doing it because everyone else is, or some weird economics is making it unprofitable to not do it.
I really don't see an issue with Pokémon moving to a DLC model. They're essentially replacing the updated rerelease they used to do (Platinum to Diamond/Pearl, Emerald to Ruby/Sapphire) with just releasing more content for the same game.
Mario Kart is also mostly course packs. Fun, but not vital.