The thing is that you're mixing up your tacos.
When I think tacos, I think Mexican: two soft corn tortillas, and meat that is pretty simply seasoned. The meat in most tacos doesn't have a ton of spices. It's just well-seasoned. The salsas take care of the spice. There are some which are a bit more flavored, but most are simple. Cumin is not a spice that features much in Mexican food, for example.
A lot of people say tacos and they really mean American: crispy shells or flour tortillas, lots of seasoning (cumin, chili powder, etc)
Different things is all.
Carnitas are Mexican. They're made with pork shoulder seasoned with salt. Then it's braised or confit with a few garlic cloves, orange (you squeeze the juice and include cut oranges as well), onion chunks, and Ceylon/Mexican cinnamon sticks, maybe some bay leaves. Once tender, you break them up and crisp either on a griddle, pan, or broiler.
And that's a more elaborate version.
At the heart it really is just pork and salt:
Michoacan style are confit:
When I make them I do the orange and cinnamon because I've gotten used to the slight sweetness from them. Like this: