Mind, the cost of heating an oven for over an hour for a couple of jacket potatoes probably doesn't make sense this winter.
I've always gone with pasta as a "Aagh, what can we have for tea?" meal.
Different shaped pastas mean the same meal looks different to the dc if it gets repeated too soon
. Then, depending on how lacking in confidence he is, either fry onion and garlic, (and whatever else you find loitering in the bottom of your fridge - peppers, courgette, spring onion, leek, etc) , add some chopped tinned toms , and simmer for a bit. This can be 'as it is' with some grated cheese, or can mix in ham, or chiritzo, or lardons, or grill and chop up some bacon, (tuna, if they didn't 'not like' it), left over cold chicken, or you could buy some meatballs or whatever for a variety on this. Alternatively, a jar of pasta sauce does the job.
Diced chicken with an array of jar sauces - Chicken tonight (or own brand) do lots of flavours, or things like a curry sauce or a sweet and sour sauce
Carbonara is easier than I used to think.
A thick soup with some nice bread
A bought pie with some chips and gravy, or some mash and veg
I mean, I LOVE our slow cooker, and it really is forgiving of an inexperienced cook. My (adult) ds swears by his air fryer - reckons you can cook everything in it. I realise this involves an initial purchase but I think the amount you save in gas / electric costs will recoup that.