It does because the bulk of the spam takes place by regular users who use their regular wallets to broadcast their spam tx to regular nodes that would then decide whether to relay them or not. When the nodes reject nonstandard transactions, they won't be relayed to reach miners and the bulk of spammers will not go through the backchannels to contact miners to mine their nonstandard not-relayed transactions.
That's not to mention that the backchannels would cost the spammers a lot more money since they'd have to incentivize the miner (grease their palm) compared to having it relayed normally as standard tx. This can act as another abuse preventive measure.

We can see that clearly by analyzing the chain and seeing that for example the standard rule on OP_RETURN size does indeed work. https://blockchair.com/bitcoin/outputs?s=time(desc)&q=type(nulldata)#f=recipient,type,time
If it were anything else, we should have seen large number of nonstandard transactions being included in blocks every day.

P.S. I also don't fully agree with the statement of "miners ignore standard rules". They don't really modify their code that much due to being too concerned about having their block rejected. Here is an example of how miners were too scared to include a nonstandard tx (a simple SegWit with uncompressed pubkey which was perfectly valid) with a big reward in their block.
The reason why an attack like Ordinals work is because it was never nonstandard to begin with.

It does because the bulk of the spam takes place by regular users who use their regular wallets to broadcast their spam tx to regular nodes that would then decide whether to relay them or not. When the nodes reject nonstandard transactions, they won't be relayed to reach miners and the bulk of spammers will not go through the backchannels to contact miners to mine their nonstandard not-relayed transactions.

We can see that clearly by analyzing the chain and seeing that for example the standard rule on OP_RETURN size does indeed work. https://blockchair.com/bitcoin/outputs?s=time(desc)&q=type(nulldata)#f=recipient,type,time
If it were anything else, we should have seen large number of nonstandard transactions being included in blocks every day.

It does because the bulk of the spam takes place by regular users who use their regular wallets to broadcast their spam tx to regular nodes that would then decide whether to relay them or not. When the nodes reject nonstandard transactions, they won't be relayed to reach miners and the bulk of spammers will not go through the backchannels to contact miners to mine their nonstandard not-relayed transactions.

We can see that clearly by analyzing the chain and seeing that for example the standard rule on OP_RETURN size does indeed work. https://blockchair.com/bitcoin/outputs?s=time(desc)&q=type(nulldata)#f=recipient,type,time