How do I clean 1960’s era greasy knotty pine kitchen cabinets?

Use vinegar and a rag.

I wrote a post about cleaning my cabinets that might help you - https://chascrazycreations.com/cleaning-kitchen-cabinets/

Dish detergent in hot water then rinse in plain hot water.

Empty freezer then turn it off. Place an open dish of baking soda and chunks of coal inside .

Fuller or GP66 degreaser

Krud Kutter might help.

Make a bucket of warm water and Dawn dish soap. Wipe your cabinets down with this solution. Dawn will remove the grease and grime. Allow to dry. Then use Murphy's Oil Soap according to directions on bottle. The soap will clean the cabinets and the oil will condition the wood.