Dry Rubs

Did you do the "bend" test? A slab of ribs, when done should fold under its own weight when lifted. If it doesn't, maybe just bows a little, its not fully cooked, and will feel tough and dry in the mouth. BBs usually take 5 hours, foiled or not, at 250.

3 hours w. a dome of 250F is way too quick. And the addition of juice in the pan really did not helpl. The moist air doesn't transmit heat as well as dry air. In a metal cooker, the water retension is not as good as in an Egg. Adding water to the cooking chamber is often necessary. But if cooking on the Egg, added moisture is best kept to added mopping sauce for more flavor, and extra time in the smoke.

Foiling pretty much guarantees tender meat. Between the foil pouch and the extra fluid, the meat rapidly braises. All of the connective tissue turns to gel. But it is not necessary. Do rub the ribs. Its not BBQ if there isn't some spice on the meat. Keep the dome around 250, and cook the meat indirect for about 4 hours. Check to see if the surface looks dry at 4 hours. If so, mop a little apple juice on then, or whatever. Around 4.75 hours, the bone ends will usually be quite exposed, and the slab with be getting hard to pick up because its so floppy. Sauce then if you want to. Wait another 15 minutes.

Should be good.

Agreed. You need a couple more hours on the smoker. Also Be sure you're pulling off the silver skin on the back of the ribs too. (try using a paper towel for tough ones).

yes. you are literally overcookingthem past the point of dryness (like a roast would be), but to the point where collagen is converted to gelatin.  the collagen no longer holds the fibers together (which is what makes a tough cut tough), and in addition it adds back the succulence that was lost when the moisture we normally expect (like in a roast) has been driven off by overcooking.

you can't get it tender until after you break down the collagen, and that means past the point of conventional 'overcooking'

a roast is already tender, so no need to get to the point where collagen breaks down  so we take the roast off at 135-140-145 or so.  if you did that with ribs or butt, they'd be tough and dry