For a significant portion of my childhood, any and all food my mom made was made in a slow cooker. There are many great meals you can make in a slow cooker, but there are also many things that should never be slow cooked. Just because you get results if you Google “crock pot pasta” does not mean you should ever get pasta anywhere near a crock pot.
Re: green bean casserole, that’s sounds similar to the logic around the “egg in the cake mix” thing. Basically, the minimum effort to make something “homemade”.