Yes, that is now the only recourse. However, on the occasions when I have gotten bad service, getting a manager during the meal would have been a challenge. I mean, when you sit at the table for 30 minutes without receiving menus or being visited by anyone, it's tough to ask to speak to a manager.
Keep in mind that I never said that I would have "cheap['d] out" on the tip. What I said was that people usually tip better for good or great service. But, when the tip is added automatically, I believe that fewer people will tip above the 18%.
My standard approach is to calculate what the tip should be and then adjust up according to the service received. But, if people haven't started by making calculations, then why would they calculate an additional 2-7% instead of just paying the bill they've been given.