Most disappointing vegetarian food is a technique problem
It is rarely about missing meat. It is about the two things meat supplied automatically and vegetables have to be given deliberately.
People who cook a vegetarian meal and find it unsatisfying usually diagnose it as an absence: there was no meat, so it was missing something. That is close to right and imprecise about what. Meat contributes two things to a dish almost without effort. It browns, generating a large quantity of savoury compounds, and it carries fat, which distributes flavour and produces the mouthfeel that makes food feel substantial. Remove it without replacing either and the result is thin, however good the vegetables.
Both are available without meat and neither happens by accident. Browning requires a hot enough pan, enough space so that the food sears rather than steams, and the patience to leave it alone. Vegetables release a great deal of water, so a crowded pan produces boiled mushrooms with a disappointing grey exterior, which is the single most common failure in home vegetarian cooking and is entirely a matter of pan size and heat.
Fat is the other half and is undersupplied more often than oversupplied. Vegetables absorb it, so a quantity that looks excessive against a raw pile is usually correct by the time everything is cooked. A roasted vegetable dish that seemed dry was almost certainly underoiled, and the correction improves it more than any addition of seasoning.
The third contributor, and the one that separates food that is pleasant from food people ask about, is savoury depth. Meat and stock supply it by default; a vegetable dish needs it added deliberately, and there is a well-established set of ingredients that do it: tomato paste cooked until it darkens, mushrooms browned properly, soy or tamari, miso, aged cheese where it is being used, seaweed, fermented bean pastes, and yeast extract in small quantities. Most cuisines with a long vegetarian tradition use several of these routinely, which is not a coincidence.
There is also a structural point about how dishes are built. A meat-centred meal has a clear organisation: a protein, a starch, a vegetable. Removing the protein and leaving the structure produces a plate with a hole in it, which is the origin of the substitute mentality, where a manufactured product is placed where the meat was. That works and it is not the only approach, and the cuisines that have cooked without meat for centuries do not organise plates that way at all. A meal built from three or four dishes intended to be eaten together, with contrasting textures and one clearly seasoned element, does not have a hole because it was never built around a centre.
Protein is the question that arrives first in any conversation about this and it is largely a matter of arithmetic rather than of difficulty. Legumes, dairy, eggs, grains, nuts and soy products all contribute, and a varied diet that includes enough total food generally supplies it without planning. There are nutrients that do warrant more attention on a diet without meat, and how much depends on the individual and on what else is being eaten, which is a matter for a qualified health professional rather than for a recipe site.
What this publication concentrates on is the cooking. The reasons people eat this way vary and are their own business; the technique is common to all of them, and it is technique rather than ideology that determines whether the food is worth eating.
One further point about how this cooking is usually learned, which explains why so many people find it disappointing. Most people arrive at it by subtraction: they take the cooking they already know and remove the meat, keeping the same dishes, the same plate structure and the same seasoning habits. That is the version that produces the thin, unsatisfying result, and it is nobody's fault, because the alternative requires learning a different set of techniques rather than omitting an ingredient. The cuisines that do this best were never built by subtraction at all.