Have you read the ingredients. Potatoes, Milk, Cod (14%) (Fish), Cream (Milk), Salmon (9%) (Fish), Butter (Milk), Wheat Flour (Wheat Flour, Calcium Carbonate, Iron, Niacin, Thiamin), Smoked Haddock (3%) (Fish), Water, Cheddar Cheese (Milk), Spinach, Free-Range Egg Yolk, Salt, Parsley, Fish Stock (Fish, Salt, Dried Potato, Sunflower Oil, Dried Cod (Fish), Lemon Juice Concentrate, Anchovy (Fish), Onion Powder), Lemon Juice, Yeast, White Pepper, Caramelised Sugar, Colours: Paprika Extract, Turmeric Extract
There's hardly any fish in it.
There's 14% cod, 9% salmon and 3% smoked haddock, so it's almost 30% fish which seems pretty normal to me? Especially when you think about the fact that fish pie also contains cheese, potatoes, sauce and other herbs and spices.
The salt and sugar content is astronomical.
It has 2g of salt per half pack, and a pack is designed to feed two people. 2g of salt per adult is a tiny amount - it's not even half a teaspoon!
I bet there would be more salt in a homemade pie than in that - think about it - smoked haddock is salty, potatoes are boiled in salted water, cheese is salty and most people add salt and pepper for flavour in their dishes too. I would bet a home cook baking a fish pie would use more than 2g of salt per person.
It also only has 3.6g of sugar per half a pack, so again, half a teaspoon or so - that's nothing. The sugar will mostly come from the carbs - so, the potatoes and the breadcrumbs.
Sugar occurs naturally in many fruits and veggies - it's not automatically the devil! Salt is also a flavouring and is perfectly fine in small amounts.