where it's pick from their standard basic offerings, or go without.
The costs to the business of providing all the options are considerable. If you really do need a "Halal salt-free low-fat", or whatever, buy your own in the terminal at departure.
Diabetic meals are ordered because of a
health condition.
And when have you seen something specifically suitable on sale airside at an airport that will cope with a longhaul flight?
Yes tailoring food to passengers' requirements does cost. But at least each passenger who eats a meal has paid for their ticket. The cost per class is hardly in relation to a similar restaurant meal on the ground ....and not providing foodstuffs could lead to far more unpleasant meals being consumed inflight (eg hamburgers/pizzas/curries ... and other fragrant items) with more gash and considerably more risks in terms of food hygiene than are implied at present.