True but then again you need to peel and prepare the potatoes, hardly onerous but it adds to the time. Once boiled you need to mash the potatoes, again not a difficult or time consuming task but again adding to the overall time.
You also need to make a bechamel sauce, again hardly an onerous thing but it adds to the overall time.
You also need to assemble said pie and bake it in the oven. All of the preparation requires active participation as opposed to just sticking a ready-made pie in the oven.
Looking at the washing up from a made from scratch ocean pie you have:
- Potato pan
- Frying pan for the fish (though I would poach them in milk and use the milk to make the bechamel)
- Bechamel pan
- Dish you baked the pie in
- Whatever you made the accompanying veg in
Again, doing the washing up for this list isn't difficult and will add a few minutes to your day but its more difficult than just recycling whatever container(s) the ready meal came in.
Then of course you needed to have all the ingredients bought and to hand.
Cooking from scratch is rewarding but it requires a lot more work and creates a lot more mess. Making a ragu lasagne properly takes all day and that's great if you have the time and even better if you can, like on the telly, involve the children and teach them to cook in the process. Real life often isn't like that and sticking a ready-made lasagne in the oven for 20-30 minutes while you get on with the ironing (or some other household task) may be more practical for a busy family.