[2022] No additional improvements to the feast buff when upgrading the farms in Ravensthorpe

I'm so confuse about the feast buff. I know that if you build facility in your settlement it will give you feast buff and if you upgrade that facility it will give you even more. But! it just stop working midway, now I have

+3.0 range damage
+25.0 health
+25.0 health
+3.0 armor.
+3.8 assassination damage
+3.8 assassination damage
+3.8 assassination damage
+3.0 Melee damage

All upgrade after this point don't give me any increased buff. What am I suppose to do after spending so much time farming all supplies and get nothing out of it.