General de Gaulle was right in the 60s that the brits are more trouble than they're worth. France is smart and won't let them back in. Brexit is now and forever as far as the EU is concerned.
De Gaulle also wanted to shield the nascent EEC from the United States's influence as much as possible. For him, integrating the United Kingdom into the EEC would have moved the EEC's barycenter too far towards Washington.