Comment by com2kid
Acid is important for meat marinades because w/o acid, penetration is just a few mm deep.
The real magic, IMHO, comes from how Indian food is spiced. Lots of contradictory flavors that are used in ways very different than western cooking. Also lots of steps involving dry roasting some of the spices, while leaving others as is, and which spices get dry roasted changes from dish to dish.
I do a lot of Indian cooking from scratch at home, and while I can slightly improvise recipes and tweak them to my taste, I am still a long way from being able to truly understand WTF is going on with some of the more complex reactions.
I do a lot of Indian cooking also and have for decades, and my suggestion is to just play around with tastes and smells. Dry roasting especially your nose is your friend. That or corner an established South Asian chef and talk to them about their use of spices :)
Acid is also really important for veg proteins because most veg proteins on their own have very little flavor. You can impart umami through various ways but umami without at least a bit of acid does not come across balanced on the palate, so you need to balance the acid with the umami.