I think the decent places give you a choice between brown or black beans. Many Islamic people might be surprised that there's lard in there AFAIK.
It's just that a few years ago you could tell that the beans had been cooked somewhat properly....with perhaps lard/oil, some onion, maybe garlic..and somebody had taken the time to actually smash a few of them, and stew them down a bit. It gave them a bit of body.
Now they are just sort of held in water....in a serving tray, and they scoop up a bit and hold them there for a moment to let the water drain off. It looks just like they are straight from the tin. Red or black....same way.
With all of the other accoutrements....the lettuce and salsa and meats and sour cream and such.....it's not that noticeable. Except that I notice it....a jejune base to an otherwise OK dish.
And like the plastic and LEDs you mentioned....it's just a little thing that to me signals that somebody there said, "Eff it, we can cut back on cooking time.....who will notice?"
Oo there's a burrito place in Cambridge? I'm not super far from there, may have to scope it out next time we go there.
By all means give it a try. It is fine......just those darned beans....
http://www.nannamexico.com/