The OP has exposed some good points, that today's modern feminist would never agree with. Unfortunately we have come to such a low point in our community that asking for just the basics from a women is considered subjecting them to slavery. A mothers/wife's first duty is to provide nourishment. That's why they are born to provide milk to their offspring and not the father. Now just because they are a little stressed with dealing babies why does that have to effect the way they cook. How hard is it to make a simple sabji taste good, especially when they live with the same person for many years and know their needs. We want to promote Dietary Vivek; how will our panth to follow rehit if their mother/wife can't provide them with simple tasty food. This will lead them to wanting to eat from restaurants and away from Sikhi.
Just whatever you do, make sure you do it with Pyaar. If you have to get a little upset that is fine but don't do it with anger in your heart rather as a way for her to take you seriously. Tell her how important her duty is and explain how stressed you yourself are with work or other worldly duties. If they still don't understand then do Ardas until Guru Sahib gives her the ability to perform her household duties diligently