If they choose that route and willingly limit the size of the junk they are injecting into the chain to 160 bit (20 bytes) chunks, we've successfully prevented spam.
An OP_RETURN output can definitely contain more non-OP information than a standard segwit native transaction, but the problem remains. People can still inject images as chunks of addresses.
You see in Bitcoin, preventing abuse has always been about making it harder not impossible. If they try splitting the data into 20-byte chunks (or any other method) that already introduces a lot of complications and they will soon face old limits, for example in this case there is the standard transaction size which limits the number of outputs that tx can have or it won't be relayed...
Nowhere near it? Lol. We're talking about people who waste thousands of dollars worth of bitcoin for transaction fees, and you think the same cannot repeat if there appears to be enough demand?
Maybe you are right but I don't think it can gain the same level of hype.