op_returns are still allowed in blocks according to consensus rules regardless of if you’re running knots or not. If you were to change that you’d hard fork bitcoin. He can’t actually remove the spam with these mempool filters. Even if every node enables his mempool policies the transactions would find their ways to miners via marathon slipstream.
Now miners go from price takers (accepting whatever fees set by users in decentralized network) to price makers, charging premiums to mine “non-standard” transactions. Now decentralized mempools and miners don’t have insight into the real fee rate. Lightning gets borked because they can’t close and settle quick enough and marathon gets extra money for being the premium mining service that mines op_returns.