The point of the von Schlieffen Plan is generally accepted to have been a 'hinge' on the Ardennes, with the strong right wing pivoting round that hinge to seize Paris. Sichelschnitt was different; originally the plan was to rerun the von Schlieffen scheme and have tanks form the mobile right wing, but that was eventually revised to the plan that was eventually used, which was a decoy movement on the right wing into the Netherlands and Belgium, and a fixing attack on the Maginot Line, while the decisive thrust was delivered through the Ardennes by the tanks, which would move straight to the sea (ignoring Paris in the first thrust) to pocket the Allied armies that moved into the Low Countries. And, hey, it worked. After that, the Germans would be in a fantastic position to debouch into France proper.
The point is that the Germans weren't really experienced much either. Outside of the Legion Condor members none of them had recent combat experience, except for the few men who were left from the old core of the Reichswehr that had served in the First World War - and there weren't many of those.
The timing issue at Sedan was this: at Sedan, the Germans of Guderian's panzer corps were debouching from the Ardennes and preparing to swing west. This was the hole in the French lines, and it was covered by only militia and levies, who even so put up a reasonably good fight. But that hole was supposed to be covered by reservists leavened with regulars, it's just that those better quality French troops didn't quite get there in time - it wasn't expected that they'd need to, since the Ardennes weren't supposed to be as easy to get through as they ended up being. I think the French were off by one, maybe two days, but by then Guderian was off on his merry romp west and there was jack-all they could do about it.
The issue was also German resolve, which was very resolute
Even after the misjudgment that was the French initial deployment--the extra army on the left to hook up with the Dutch, the drive for the advanced position at the Dyle River, the weak Ninth Army holding the Meuse through the Ardennes--that left the French vulnerable to disaster should the Germans break through at the Meuse, the French *should* have been able to recover. The Ninth Army was weak, but the Meuse was a strong position. And once it was clear that there was a major attack through the Ardennes, the French Army was not that slow to respond.
We can track the French reaction to the Nazi attack across the Meuse. The first thing to note is that the Nazi lead elements took up to 70% casualties and kept coming--indicative of extraordinary ideological commitment. In a world in which any "normal" unit breaks at 25% casualties or so, it's hard to beat people who keep coming at you: you can only hope that the enemy doesn't have that many of them. Had the Nazi soldiers been "normal," the initial attack by the seven panzer divisions would probably have failed, and the French would have had time to redeploy.
"Gamelin and Georges on the morning of May 13 were keeping their eyes out not only for the great battle in Belgium but for... German forces debouching from the Ardennes and attempting to cut behind the Maginot Line..."
Thus three divisions from the general reserve were fed into the Meuse line on the 13th of May, and the French high command clearly knew it was a trouble spot. By May 15, the French First Armored division had been switched from the Belgian plain to the Ninth Army sector, infantry formations had been ordered to assemble behind the Ninth Army to form a new Sixth Army, and the Second Armored division had been ordered to assemble in its sector.
Within a few days later Charles de Gaulle was placed in command of the Fourth Armored division and told to attack the southern flank of the German breakthrough.
So what happened to all these forces--four heavy armored divisions with perhaps 800 tanks between them, plus a large chunk of the sixteen infantry divisions that were in the French strategic reserve on May 10?
Well...
... The First Armored division ran out of gas. While it was waiting for the fuel trucks to come up to refuel it, it was attacked by Rommel's panzer division and destroyed as a fighting unit.
... The Second Armored division... according to Shirer: "Orders for the [second armored] division to move... did not come until noon of May 13.... The trains with the tanks and artillery were not able to start until the afternon of the 14th.... The wheeled vehicles with the supplies ran into the panzers racing west from Sedan and, having no combat elements, withdrew south of the Aisne.... The tanks and tracked artillery were finally uinloaded from their flatcars... between Saint-Quentin and Hirson.... The division was hopelessly dispersed over a large triangle between Hirson, La Fere on the Oise, and Rethel on the Aisne..."
... The Third Armored division retreated to the south as General Huntziger had ordered: he thought its principal task should be to guard the Maginot line against a flanking attack should the Nazis turn south after crossing the Meuse
... The infantry formations of the Sixth Army were overrun by Reinhardt's Sixth panzer division on May 15 and 16 while they were trying to assemble.
By May 16, as Shirer puts it: "The three heavy [armored divisions] the French had, all of which in May 10 had been stationed... within 50 miles of the Meuse at Sedan and Mezieres, which they could have reached by road overnight, had thus been squandered.... Not one had been properly deployed.... By now, May 16, they no longer counted. There remained only the newly formed 4th [armored division], commanded by de Gaulle, which was below strength and without divisional training..."
Now talk about bad luck, and I believe this led to timing issue your suggesting. The French could have and should have had troops in sufficient numbers to block the German advance. And with the weakness in German armor, and the benefit of a strong position like that at Sedan, could have turned the tide. But it seems the French were always one step behind, their communications system was obsolete to mobile tank warfare. And also in war luck plays a part, and France had no luck.
But in reality, the Allies were superior to the Germans in men, artillery, tanks and aircraft. So why did the Allies lose? Germany was superior in its conduct of battle - strategically, operationally and tactically. And as good as Germany was, France and her allies were equally bad, strategically, operationally and tactically. But the Allies I believe lacked military imagination, and were simple minded when it came to the evolution of warfare. They were, and I here the term static defense, too defensive minded, which is exactly the way they fought and thought. Was it not Napoleon who said, "An army that stays inside its fortifications is beaten." He was right