A young company called Scratch is about to launch its own species of ready meal in Sainsbury's. All the ingredients for dinner are in the box: the chicken tikka masala contains meat, curry paste, tomatoes, yoghurt and rice, with simple instructions to put it all together. They're supposed to feed one person – it isn't a huge portion – and they cost four quid, meaning the cost would be ridiculous for a family of four.

"Recipe by Michel Roux" each packet says, and I wonder if they fail to specify senior or junior because the recipe is Sr's, and Jr's profile is bigger nowadays. I respect Michel Roux Sr, but Scratch is not good food. (The Rouxs, of course, have some experience in ready meals: they used to do M&S's.) And the packaging appears to be lacking in green credentials with the rice in its own plastic, the little sauces in plastic tubs, the whole encased in a segmented plastic box.

There's more and more of this sort of thing around. A German company called Hello Fresh reached the UK a few weeks ago. It works along similar lines to veg box delivery schemes, except it includes all the food you need for a week with recipes and in the right portions, so theoretically you don't have to go to the shops at all.

The Old El Paso kits which we all enjoyed as kids have now been joined by Thai, Spanish and Japanese versions. At the most basic level, these kits are just glorified spice selections. Ainsley Harriott sells spice kits for north African meatballs and stew, while companies like Spicentice and Secret Chef do the same thing rather better.

Even if you have to buy the perishable stuff, kit meals have obvious benefits. They're convenient and straightforward and make life easier for harried shoppers. If you've never cooked, say, a curry before, and think it unlikely you'd do so again, then a sachet of spices that might feed two or three people is preferable to buying large jars that'll soon go stale. And if you don't know how to cook at all but are trying to learn, packets and labels should hold your hand as effectively as might Delia.

I'm not sure these kits are much use for other people. Committed cooks have well-stocked spice racks and storecupboards as well as a repertoire of dishes they can make without a trip to the shops. In the kitchen, convenience often means an inferior product. Swanson's TV Dinners arrived in the US in the 1950s, and to judge by the photographs they really were regrettable food.

I've never tasted an interesting or notably enjoyable ready meal. Kits imply a rigidity that seems unappealing in the modern kitchen. Many people will assume that the spice mix is fixed and unimprovable, when in fact a little cardamom or some judicious fenugreek could improve things considerably. Convenience means compromise, in short, and compromises never satisfy anyone.