I'm with Dave--the ribs were likely undercooked.
'Dry' can also signify underdone. This is because internal rendering has not occurred to a point where the connective tissue has rendered/gelatinized sufficiently. Lacking this, the meat's texture feels dry in the mouth. It's also somewhat-to-very chewy.
Next comes 'done', where there has been sufficient rendering/gelatization of interior connective tissue and pockets of fat. The meat is moist and tender. I'm not a fan of the tear test because I like the racks whole till serving time but no, little effortr is required if that is the approach you use. I prefer inserting a temp probe between the bones--it goes in smoothly with little to no resistance. In both cases the sufficient internal rendering allows the meat to give easily--either during tearing or when the probe is inserted. Yes, the meat is softer at this point.
The next level, overdone, occurs when the meat cooks past the done point. Sufficient rendering has occurred but the meat has cooked too long forcing any remaining water to evaporate and the rendered tissue/fat to drip away. The meat feels dry in the mouth. It's not 'tough', per se; it usually feels kind of stringy. It starts to lose its softness though. With much of the rendering gone, there isn't much there to lubricate the meat nor, significantly, the tongue and mouth.
Ribs and brisket especially (but many other meats as well) are best cooked to a point of tenderness that one feels for, not cooked by time nor to a particular internal temp. Time can tell you when it's likely you should start checking for tenderness--and a specific internal temp can tell you the same thing, i.e., when to start checking--but neither time nor temp beats checking yourself. Time and temp might correlate with 'done'--but they might not.