*Possible* - I don't know if it fixed all the possibilities, but it certainly addressed the main one that was being abused.
Please do your homework and read either this thread or the mailing list discussion (at least the first message there). One has to repeat and repeat things like a parrot it seems 
As ABCbits already wrote the main problem is that besides from OP_RETURN there are more harmful ways to store data. The way you mentioned (Taproot witness abuse) is only slightly more harmful than OP_RETURN, but the remaining case, fake public keys, is the real problem -- if we had a real spam wave with these techniques, this could become a serious problem for decentralization due to UTXO set bloating.Calm down, my friend. I'm just intrigued that, even though there is obvious exploitation and a known fix for one of the ways the network can be spammed, some people are still against taking any action because - you know - it's "permissionless," so we should allow whatever spammers want to do with the network, as long as they pay the fees.