Apologies if I was mistaken, but my reading was two hours to Dragon Island, meaning to Dragon North terminal. I found your 70 min quite reasonable, and that assumes a 10 min wait for the train. Maybe the OP will do it in 80 minutes, at most 90.
I read your post as suggesting to schedule an "absolute minimum" of 2 hours between the hotel and reaching the gate (so add another 15/20 before gate closes).
That seems quite conservative to me. (if e-gate and no checked luggage).
I dont see how it could take more than 90 min from leaving hotel (Kowloon AE) to reaching the departing gate. Then you should arrive before the gate closes, say 15 min or 20 min before depart time. That's why I suggested a total of 2 hours before departing time, not to reach Dragon Island.

The major uncertainty is checking out at Ritz: wait for lift, line at check out. That's why I mentioned "leaving from hotel", rather than "leaving from your room".