This is knots propaganda that is technically false. door is already open: there is no consensus limit on op_return and it’s trivial to route around filtering nodes. It’s just not done because there are cheaper ways to store large images (inscriptions), which there are already is massive abuse of. For reasons why it was done, this post by sipa explains it clearly

Bitcoin Stack Exchange

Implications of OP_RETURN changes in upcoming Bitcoin Core version 30.0

As you may know, there has been a debate around the upcoming release of Bitcoin Core. I hear the arguments against it and I agree that Bitcoin is m...