When they want a champ to be "meta" or just about to release new fancy skins for him/her, it is okay as they did that on purpose (e.g. Zac). When they really broke the champ by accident and they have no business interests either atm - like Singed, Sona, etc. - then they will nerf it in 1-2 days.
But I don't think in the current situation Ezreal is the problem. It's the same thing like enchanters and Ardent Censer was. The problems are the new runes, in this case mostly Kleptomancy. Balance was quite okay around 7.20 so it would be a much wiser idea to fix the runes themselves before touching the champs who can exploit them this much.
Though, don't worry, they will nerf the champs, then fix the runes, then fix the champs who will become OP at that point, then they will start it again :)
They do this on purpose and they don't want and will never make any real balance. There will be some more or less okay state around the next Worlds what they will ruin in next preseason and start the whole nonsense all over again. Just as always.