"Frexit without Brexit isn't the end of the European project."

Yes it is.

Britain has always been semi-detached from Europe. She was invited in at the beginning, but rejected it "Because the Durham Miners wouldn't like it". 

Even after the UK joined, it sort for itself exemption after exemption, after exemption.

For France it was core to their post war identity, the ability to project French influence using German economic power.

Brexit is a hit, a palpable hit to the EU (UK is the third largest contributor after all) but without France, their is no EU.