It's not as hard as you might imagine. Cheese is great because it's an umami bomb. However, there are other umami bombs out there (tomatoes being one!). As many people have said, though, it's all about the knowledge. A miso garlic sauce is insane, and easy to make, but very few people outside of Japan know about it. I'm not really sure exactly where the umami gets in, but fermented hot sauces are also amazing for filling out flavour (it could be the fermentation). To cook good vegan food it's not actually much harder, but you practically have to learn to cook all over again. (Was vegan for 10 years... hopes people enjoyed my cooking as much as I did... no guarantees ;-) ).