Two other factors to consider:
1. What's the big hurry to shut down an engine? Is Air France procedure to shut down a failed engine immediately after takeoff? Or was this the Flight Engineer's individualized procedure?
2. During an emergency, the usual simulator training scenario concludes with a successful return to the airport, or a landing at one nearest "suitable" airport!
That training "mind set" obviously had influenced Marty and his crew to head for Le Bourget 10 miles down the road, a reasonable decision if the airplane were still flyable.
But the airplane was at 200 feet, gear down, one engine shut down, one engine producing intermittent thrust, and airspeed was decreasing.
Obviously it's unthinkable and unimaginable for a jet crew, much less a Concorde crew, to deliberately put the jet down in a field or on a highway whilst there still is some control. And with Le Bourget in view it was Marty's instinctive reaction to continue to extract performance from the jet.
The airspeed indicator (referenced three times by the F/O on the CVR) was the chief instrument upon which Marty should have relied upon to make the ultimate decision to put the jet down immediately. A controlled crash, as opposed to a stall and assured death. But Marty hesitated. It's not a decision which would have required time or thought, only immediate instinctive reaction.
The first important lesson a pilot learns when flying a single engine trainer: If the engine quits right after takeoff, don't even think about making any turns, land straight ahead!
When flying a crippled multiengine jet, crash land before stalling at any cost.