I've managed to get great, fall-off-the-bone ribs out of a crappy gas grill, it just takes some patience and ingenuity. First, a good wireless grill temperature probe is a MUST. Clip the probe onto the grill rack near your meat. Adjust the gas down until you're at approx. 225F. As my grill doesn't have good vents, I had to turn the gas down all the way, and insert something to lift the lid a crack. This kept my temperature down enough but made the temp vary due to breezes. So long as it didn't stay sustained above 240F, I didn't mess with it further. You definitely want to keep it above 212F. A single rack of baby backs cooks in 3-4 hours this way.
I had to travel with my ribs, so after 4 hours, I wrapped them in foil, and 30 minutes later put them onto direct heat and sauced them. Additional cooking time on direct heat was about 15 minutes, enough for the sauce to carmelize, reapplied sauce and carmelized again. Then I put them back into foil and left them for another 20-25 minutes. I unwrapped them and cut into single rib pieces and realized I'd accidentally managed to make fall-off-the-bones ribs, and won 2nd prize at the neighborhood cook-off my first try.
Next year I'm going for the "real" grill equipment, but it CAN be done with the most basic tools, if enough care and patience adjusting the temperature is used.