If I had to distinguish Taco bell from, say, McDonalds, I would say that Taco bell has the advantage of being filling but not putting you in a food coma.
One of it's biggest unsung heroes is the bean burrito; It avoids most questions about the meat and has been a popular option among folks who wanted to avoid meat in their diets. It's... almost healthy. Almost.
Taco Bell would be if a large corporation operated a bunch of kebab shops, but used the absolute cheapest ingredients possible (with said ingredients largely being precooked and prepackaged such that anyone with so much as basic motor skills can slap a kebab together in 15 seconds), "Europeanized" it until there's only superficial resemblance to a kebab at best, and then sold it for similarly cheap prices from drive-thru fast food restaurants.