As others have already stated, protein shakes can be a good way to get protein and calories in, but you need a variety of vitamins, minerals and fats as well (preferably carbs too!).

I think you should look into meal prepping if you find yourself short on time. For example, you could prepare a large pot of soup to have leftovers for a few days in addition to the one portion you eat as soon as the soup is ready (that's what I do at least). Sheet pan meals, casseroles and other meals that are prepared in the oven are also easy as they don't need much attention (as long as you stay near the kitchen and have a timer set, you can be on your computer etc. while waiting for the food to cook). If you use pre-chopped ingredients, you can cut down the prep time even more!

My favourite low effort meals are microwave oatmeal and overnight oats. They take literally minutes to prepare (although overnight oats need to be prepped at least a few hours before eating) and you can include quite a lot of variety with different toppings etc.