Plus if an individual does decide to upgrade his/her node, isn't the part of the block where the data resides by way of OP_RETURN prunable? That's probably better than embedding data where it can be a long-term problem for the network, no?
AFAIK there's still no full node software that allow prune only OP_RETURN output. Besides, it doesn't change the fact you still need to download and verify whole block first.
I believe that Bitcoin-Stamps use OP_RETURN. The dick pics and fart sounds on the blockchain lovers will start minting using MikeInSpace's "protocol".
Bitcoin Stamps (also called SRC-20) actually use P2MS. Here's the proof,
https://github.com/stampchain-io/stamps_sdk/blob/main/docs/src20specs.md.