My wife and I gave Blackstone a shot recently, and I have to say that I'm a little underwhelmed. It was FINE, but based on reviews I'd read I have to say that I expected more.
We got a pizza with half Street Taco, and half Vegetarian, and I must say that the highlight, much to my surprise, was the veg half. The vegetables tasted really fresh, and delicious. The Street Taco half was really bland... If I'd been given a slice of it, in some form of taste test, I'm not sure that I'd have been able to tell what the intention was. It was simply BLAND.
In my opinion, if you're going to make a taco pizza, the meat has to be fairly well seasoned. I picked up a few pieces of carnitas off the pizza, to taste them independently, and they tasted like... nothing. I certainly don't care what kind of meat they use, but I want to taste taco on a taco slice... and I didn't. The only taco-y flavor is a salsa they give you on the side (couldn't taste the sauce under the cheese either). If you don't put salsa on the slice, it won't taste like it's inspired by Mexican food at all. My suggestion - either season your carnitas a little more aggressively, or switch to something like Barbacoa to spice it up a little.
I'd love to try Blackstone again. I want to like it, as it's so close to our house, but based on our first experience I'm not running out the door to get another pie here.