The small, mostly non-paved roads through the Ardennes were actually a severe bottleneck and slowed down Wehrmacht considerably, so the French got it half right. If they had not stuck to the belief and had reacted faster, the entire offensive could have been stalled then and there.
Regarding the French tanks, they were still designed with a rerun of WW1 in mind. Heavy armour is nice if you expect frontal attacks on fixed positions or defend a fixed position yourself. Of course, speed is of minimal importance in such a role. Plus, if you are not manoeuvering much, you can dispense with the radio which is just expensive and unnecessary gear, it takes space inside the tank and might require an extra crewmember. Also, since you are not manoeuvering much, you don't need to be able to drive long distances range-wise or service-wise, just to support a charge across the no man's land before stopping and waiting for the battlelines to shift and the logistics train to catch up.
In a tank-to-tank fight, the French tanks would give a beating to the Germans. And they had more tanks than Germany, PLUS what the BEF would bring. But the crafty Germans had made their Panzers fast, mechanically reliable (before they got the fascination with heavy tanks) and with radios (to coordinate a large fast-moving force), so they simply outmanoeuvered and outran the French tanks, leaving infantry, 88s and Stukas to deal with them. The German used the tanks to zip through the front lines and wreak havoc among the rear echelon which was completely defenseless.
The irony of the situation was that at the time of surrender, the French Army was still largely intact (Dolchstoß much?), except that it was completely in the wrong place with no realistic chance of getting itself in time where it should have been, and had its supply lines cut by the fast-moving Panzers.