these items rely on the goodwill of the people who make the games

But they rely on the goodwill of the game devs regardless of the items being NFT-s. Patches causing meta changes is a regular thing without NFT-s.

someone who is both a dev and has a lot of certain NFTs could attempt to make the in-game item busted or required for competitive meta in order to sell

Or just do the same and sell the card in the in-game store for lots of $? As lots of mobile games do.