You were obviously dropped on your head as a child if you can't acknowledge that a DPS class dealing burst damage better than a burst class is a bad idea, because it removes all reason to bring a burst class. You cannot dispute this, as it is fact. If I have a mage and a marksman, and the marksman not only does as much damage as the mage, but isn't gated by resources like a mage is, there isn't any reason to bring the mage over the marksman.
You would get what you have in this meta (where people generally have at least two ADCs), where mages only exist to use Ardent Censer to make ADCs do more damage, since ADCs do just as much burst damage as mages right now.
The meta team comp right now is 2 ADCs, an Ardent Censer abuser, and 2 tanks. You don't even really need a real source of AP damage that much because tank items are basically useless against ADCs, who will shred through a tank with ease while sustaining harder than Vladimir, despite having GW from Thornmail.
This is what you get when ADCs are good, and it's not a healthy or fun meta for anyone but ADCs, which, judging by your retarded biases, you are clearly one of.