The ruling on Schrems II (the court case that struck down Privacy Shield) did not state that SCCs on their own would be sufficient. It said that SCCs + "additional safeguards" would be allowable. There have been several rulings already that SCCs on their own are not sufficient.

The "additional safeguards" must include a risk analysis of US access to EU residents' data. Every court case I've seen from Schrems II onward identifies the US CLOUD Act as the privacy risk to address. CNIL is basically ruling that you cannot transfer data to a US company subject to the CLOUD Act, and an SCC cannot deal with that. This still leaves open the possibility of using US services that are not subject to the CLOUD Act. This is consistent with all rulings to date.