The hardest part of cooking on a weekday is often deciding what to make. A short plan on Sunday removes that question for the whole week.
Pick five dinners you already know how to cook. Mix them up: one pasta, one soup, one tray of roasted vegetables, one rice dish, one night of leftovers.
Write a single shopping list from the five and buy everything in one trip. Cook a little extra on the busy nights so the leftover night takes care of itself.
After a few weeks you will have a rotation of favourites and much less time spent staring into the fridge.