Legumes, properly cooked

The difference between dried and tinned is real and so is the convenience.

Legumes are the practical foundation of most vegetarian cooking, and cooking them from dried produces noticeably better texture and a cooking liquid that is itself valuable. It also requires planning that many people cannot reliably do.

Tinned are entirely legitimate and are what most weeknight cooking will use. They benefit from being rinsed, and then from being cooked further in the dish rather than added at the end, so that they take on seasoning rather than sitting in it.

For dried, the main variables are age and salt. Old legumes never soften properly regardless of cooking time, which is the usual explanation for a batch that stayed hard. Salting the cooking water is now generally regarded as fine and improves seasoning throughout.

Cooking a large batch and freezing in portions is the arrangement that makes dried practical for people with limited weeknight time, and the cooking liquid freezes usefully alongside them.

It is worth adding that the cooking liquid from legumes is genuinely useful and is routinely discarded. It carries flavour and body, it improves any sauce or soup it goes into, and it costs nothing since it is a byproduct of something you were making anyway.