Fast Castle can be punished by a more aggressive Feudal approach. Small walls might stop scouts, but they don’t stop archers. Consider this, Camels have nowhere the amount of stopping power as a Knight, and they can be killed by even Feudal Archers with fletching because of their 0 base pierce armor. A FC can only make so many Camels because of their poor food eco and getting kicked off gold means sure death. If you anticipate a FC opening, pivot to the pocket and punish them hard. The flank can hold off the enemy flank by mixing in a few skirms, because the pocket isn’t making scouts to punish.