Is this game always so hard? (doing Cleansing of Loire)

Hi

I played this game a lot when I was like 12 years old for the first time, but I don't think i ever beat the whole campaign.

So I just returned to it and I'm struggling with the French campaign at Cleansing of Loire.

I've been sending tons of pikemen and crossbowmen and battering rams, i managed to destroy two castles out of three but the enemies seem to have now joined forces against me, they're sending a lot of knights, i'm holding up for now sending one party after another but i'm running out of gold to make rams.

So am I screwed? I've put 3:30 hours into this mission, it's a bit frustrating to nibble away at their buildings hoping i'll be the one to have more resources, which i doubt.

Does it get even harder in later missions?