and as far as economic incentives go,

what incentive do I have to relay ANY transaction that isn't my own?

I am incentivized to keep Bitcoin running smoothly so my own transactions are relayed and mined.

That means not bifurcating the network by ignoring otherwise consensus-valid transactions.

I dont see how I have any economic incentive to relay other peoples monetary txs and ignore large op_returns.

except I don't like them and think they're spam, which isn't economic.