We have had multiple phases in Bitcoin’s history in which colored coin protocols, NFTs, or other schemes started using Bitcoin as a data layer. While some of them temporarily increased demand for blockspace, the mempool has so far always emptied eventually. Currently, the one-week average feerate in blocks is below 4 satoshis/virtualbyte.

OP_RETURNs are more expensive than inscriptions for larger amounts of data, and the data payload is not subject to segwit’s witness discount. Previous uses of OP_RETURN were shortlived as they became to expensive for the operators and either switched to other networks or were optimized out of existence. It is not clear to me what scenario the writer is picturing in which loosening the OP_RETURN limits would lead to a substantial amount of OP_RETURN data that could be classified as "opening the shitcoin floodgates".