most of the groceries the SO and I buy end up going bad before we can use all of the ingredients.

So what you mean to say that for YOU it's cheaper to eat out given your current eating and cooking habits. But you are generalizing this for everyone. There are lots of reasons buying groceries and cooking may not be working for you. If you really want to save money, there is absolutely no question that it's cheaper than paying someone to cook for you every meal. Just because you haven't figured out how to do that doesn't mean you can say that's universally true.

This said, it sounds like eating out all the time is working for you and you are happy with it.

So this may not apply to you, but... If you do want to optimize for cost, I'd suggest:

1. Don't buy cheap ingredients. Discounted groceries are old groceries. Buy from a farmer's market if you can as things are WAY fresher and will last much longer.
2. Work out a small set of meals that you can put on repeat, last long and/or freeze well. Make these in quantities for several meals.
3. Buy as your base ingredients things that aren't perishable or can be frozen easily. Dried beans are an obvious example.
4. Pool food resources with friends.