If enough people run nodes that filter out op_return larger than 80 bytes then miners will have less incentive to include that arbitrary data in blocks.
In the case of a miner mining a block with arbitrary data that most nodes do not have in their mempools because of filters, that block’s propagation will be slower meaning the miner has a higher risk of the block going ‘stale’. This is a real risk and is why Mara Slipstream cost 2x the fees of the normal p2p network.
