I think everyone undercooks their first racks of ribs.
It takes some trial and error based on what you like. I've settled on 5 hours no peek for baby backs. I also like to rest wrapped in foil for 1 hour. That's works for me, because I like to serve them "dry rub" style, then serve sauce(s) on the side. With the 3-step method, and total of 5 hours (2-2-1) is probably going to come up a bit short, because the ribs, as well as the smoker, are cooling off between steps, and it takes a while for the meat and the smoker to get back up to temp. You might try 3-2-1 next time and see how that goes.