Being in a coalition does not let you break truce without penalty when attacking the target. When there are 3 or more nations with AE against you in a coalition against you and not in a truce with you, they can get the CB and attack.
If you piss off half a dozen to a dozen nations at a time, yes, they will end up launching continuous and staggered coalition wars due to truce timers. Whoever you were just fighting with that you peaced out on will probably join the coalition, but can't attack or join in for 5 years. Then a bunch of other unrelated nations join in and start their own war against you. And a bunch of nations who were busy fighting a different war will join the coalition upon the ending of that war, then start one against you.
The coalition CB is working just fine. Make smarter moves. You made too many people angry. Surrender, cancel a vassal, release a nation, give back a province. Only way you're going to drop a lot of people out.