op_returns don’t get the witness discount. If people started spamming them the total size of the block would be smaller (up to 1mb) compared to a potential of 4mb for txs that get the witness discount (inscriptions, segwit txs, etc). The utxo set would be smaller as well since op_returns are provably unspendable so they can be removed. All of these things make it easier to run a node: slower growth of disk space requirements, quicker validation. Not saying that blocks full of these would be a good thing, just saying they wouldn’t make running a node harder, it would make it easier.