That is what I meant. I do not make my own rubs, and I really don't make my own injections. I take the sodium phosphate, add X rub (or salt and pepper if it is that simple), add water or beef stock,(whatever), mix and inject! The sodium phosphate is pretty neutral in flavor, at least for me. it just helps with distribution of the other flavors throughout the meat, and as you mentioned, it keeps it moist!
...but as for now I dont have enough experience on what would make good flavor profiles. The smartest thing iv done in the last year was getting away from me making my own rubs and using commercial rubs pros win with.