Like other people have said, you only get the 30 minute penalty if you've cancelled queues a few times in a single day, so that sounds like a you problem.

Though, on the subject, I got screwed out of a queue once because I happened to teleport to Limsa and it popped while I was in the loading screen, and of course with everyone crammed in there it took too long and I had to re-queue. There should be some kind of "please wait I'm here I just can't ready up" button you can press while otherwise engaged. Even if it makes you load in to the duty slightly later than everyone, at least you'd make it. That loading screen taking so long wasn't even my fault. Luckily I didn't get a penalty because it was my first drop out of the day, so I just re-queued and moved on. Something OP should consider.