Has anyone beaten the game? It took me a few playthroughs to figure out what to do, but on my current playthrough by day 50 I had eliminated both gates on the right side and one on the left. Now I'm on day 62 and I can't make any progress against the last gate. I have hundreds of archers, both catapults, all the knights, using all the shrines, etc....yet the game just sends so many damn monsters at me that I can't make any headway on the final gate.

You can win.
Try to attack the portal after bloodmoon.
Your king will have to help throwing gold in front of your knights and possibly distracting the trolls by running through them, so that they follow you.
Also, portals don´t heal, so maybe you will have to attack more than once before destroying it.
But beware, after you have destroyed the last portal there will be a last heavy attack, you will have to survive.

I tried that tactic multiple times with no luck, then after I sent my knights in expecting them to die, I ran back to my castle to recruit more knights and miraculously won. It's a fun game, though I'm not sure about replayability without some updates.

What ever you do, do not end the game at night. Can't save! The way I stopped the game from ending is running through the Hulk and have him follow me away from the archers until morning and then I got him back so they can finish him off.

I was in the same situation as you. Where I didn't have enough to attack on the morning after the bloodmoon and by the time the knights got to the end of my empire 2 days had past. I timed it so the knights would get there after a bloodmoon and eventually took down the last portal.

Finally that last update mentions reduce the rampup of enemies after the 24th day.