I’m catching up with how Ordinals work. This seems relevant:

“Inscription content is entirely on-chain, stored in taproot script-path spend scripts. Taproot scripts have very few restrictions on their content, and additionally receive the witness discount, making inscription content storage relatively economical.”

https://docs.ordinals.com/inscriptions.html

This same thing exists in Bitcoin, which is why Ordinals use witness data instead of OP_RETURN.

You can think of Monero's tx_extra as being similar to OP_RETURN and having similar caps in size.

There is no reasonable way to prevent arbitrary data storage on-chain through steganography, it has to be possible for other "real" use cases to work.

The only real pain is that they don't pay full fees due to segwit discount, other than that it is what it is.