Well yes, French and Polish tactics were obsolete (fun fact: the Maginot line actually did what it was supposed to do, driving the Germans to the North, but the French fucked up by thinking they would not advance through the Ardennes mountains), and the British forces in France were undermanned and under-equipped (IIRC the Battle of Arras featured almost all the British tanks in France, like all 40). The USSR early in the war was in a bad shape in terms of combat doctrine (their greatest officers were 1. dead, 2. in the gulag 3. in the Far East preparing for another Japanese invasion, their divisions were organized into peace-time districts and not in defensive positions) but they really improved throughout the war.

Actually, tanks being infantry support still stands, it is the infantry that holds ground, what changed was how the tank as a support weapon should be used, not spread out throughout the front lines so you've got a tank every 3 km (that's how you have the stories of single French/Soviet tanks stopping whole armored columns but ultimately overwhelmed), but instead concentrated into flexible units which can quickly redeploy wherever they are needed.