Ordinals are an arbitrary ownership scheme with little to do with Bitcoin, you're referring to inscriptions here which can be defined as transactions which escapes arbitrary data into the witness portion of a transaction

What do you mean by valid? Inscriptions are Bitcoin transactions that circumvent Bitcoin "spam" filters which are put into place to encourage users to make transactions in ways to not bloat the UTXO set. It takes a mechanism (witness discount) meant to encourage users to utilize multiple utxos more efficiently into a mechanism where it generates unprunable dust outputs. Arbitrary data on Bitcoin is valid (hence OP_Return is offered), but having it unprunable and not paid-for-in-full is a harm on the network because it puts a cost on node operators and outbids for non-arbitrary data storage-use for blockspace. As an attack it's actually pretty smart (not stupid) to hide behind people like Mr bailey and the silly dancing wizards 🤔

But whose to say what is spam as long as someone's having fun? People are free to create whatever transactions they want, and the mechanism of used in inscriptions is just one method -- there likely will be more methods in the future. Oh heavens, a never ending cat and mouse game, the horror🤦 Is it already time to do nothing?

Every class of Bitcoiner gets to ask the question: "should users be encouraged to spam/scam the network?" then do something about it (even nothing!)