I know. It sucks. That's why so many people are ditching these types of gyms if they are into barbell training. It's a better investment to carve out a corner of your garage with a good rack and just train at home. Or perhaps find a Crossfit gym that has some open gym hours for you to go and use their racks.
You are right though. You can't hog the rack for 30+ minutes. Can you go at like 1pm? Gyms usually empty in the early afternoon