Everyone knows how frustrating it is to come out of GA only to be completely useless because the enemy Caitlyn put down a trap or the Morgana threw out a premature bind. When this happens your GA animation and the time it takes the enemy team to inevitably kill you is only short time-waste for your team to run away or go in before the enemy team seek their next target.
Because this happens often, especially in higher play, surely it would be nice to add a 0.5-1 second CC immunity window so you have a slight chance of escaping and making your GA worth it instead of being chain CCed to your death with no escape?
Even QSS or cleanse can't help much when the enemy team throw all their CC at the same time.
tl;dr It's too easy for the enemy team to kill you with CC after GA so a 0.5-1 second CC immunity window would be nice.