yea, in the end it all comes down to doctrine and advanced tactics. The pzI and pzII might have been outdated relatively quickly but still performed very good due to excelent tactics.Compare the specs of the FT-17 to the Panzer I, Panzer(38)t and T-26 and get back to me.
Germany didn't have a better tank then the FT-17 until the Panzer II series A entered production in December 1937, two years into the game timeframe. If the Panzer I was good enough for combat duty, the FT-17 was.
The part where the ft-17 lacks is the offensive tho, 8kp/h offroad and 20kp/h on road with an maximum range of 40km pretty much limit it to defensive usage. You certainly wont invade other countries with it but give the enemies infantry a hard time.