what to do when you rush their flank as flank and you basically make him irrelevant but then their pocket knight rushes you over and over and your pocket is just wanking?

title

had a 3vs3 where i basically made their flank completely irrelevant for 30 minutes, he was still in dark age at 15 minutes, problem is, since i raided him hard, i couldn't obviously fast castle

so his dude on pocket on huns just fast castles and runs me over and over with knights while i'm still feudal, and i just can't do anything because i made sure to raid his flank and couldn't fast castle nor raid him

my pocket doesn't do shit to prevent it, doesn't even raid their pocket as response

what to do?

just don't rush in teamgames?