once claimed that the word umami in Japanese
literally means 'delicious savoury flavour'.
It remains to be seen whether scientists will ever agree on the existence of other taste elements besides these five; astringency and especially fat are considered strong contenders. The idea that there are only four held on for an amazingly long time, when you consider how flavourful mushrooms can be, for instance, without being notably sweet, sour, salty or bitter, and without having such a strong smell that you can plausibly explain their taste that way.
Meat meals often taste pretty umami because the presence of lots of protein is strongly correlated with glutamate and the other amino acids behind the umami taste. For vegetarian meals, it's often a good idea to include a natural source of monosodium glutamate or glutamine to fill out the flavour, like mushrooms, celery, soy sauce or vegetable stock.