Ready Meals - are they really that bad for us?

There's no doubt there are some delicious pre prepared meals for sale in the shops these days but we are lead to believe that they are bad for us because there is too much salt or sugar in them. But are they really so bad when many people add too much salt to their cooking anyway?
I am not comfortable in eating fast food meals because of the preservatives. It may be only in my mind but it is better to be sure. If you know instant noodles that you just pour hot water and that's it, I never eat that. Based on my own research there are 5 people I know who developed kidney problems due to eating instant noodles frequently.