If they do an inspection, you better have it disabled. They don't discover you using it, they discover it being usable, which is a violation and fine.
Yes, it's annoying having such systems and not being able to use them. Most of our cruising is coastal and we run outside so discharge, even treated, 3+ miles offshore. We do use pump outs when we stay places for a while. We used pump outs more on the inland portion of the loop than the entire remainder of our boating. Very seldom reached a marina where the pump out wasn't working and it was only a short time and they were very apologetic.
Someone mentioned reviewing on Active Captain. I'd add to that, hold marinas accountable. Ask in advance and if their pump out isn't working, don't give them your business. Make sure they know what it's costing them. I've heard you give them the business over showers and restrooms, do it on pumpouts. Buy your fuel only at marinas with working pump outs. Call in advance and ask. Write their owner. I know a group of owners went on a letter writing campaign over several matters, writing the major marina management company's corporate officers. In less than two weeks, someone from corporate was onsite, the dockmaster was gone, and the items complained about were all being worked on. Post a Google or Yelp review too. If the manager won't fix the problem, go over their head. If it's municipal and the operator isn't taking care of it, go to the town managers. Last thing they want to be getting calls on is pump outs.
It's fine to rant here, but if that's the limit of your ranting, then you're not doing anything toward improving the situation. Do more.