Why do people keep saying AP is weak and gets nothing?

EDIT: forgot to mention mages have cc ulitity I don't understand why people use "ap values have gone down" so this must he ap champions are inferior to AD. This is in fact FALSE. AP comes in larger chunks than AD. You never see an AD item that gives 100 AD do you? AP still does damage. I don't understand peoples arguments. 350 AP on a champion is still significant damage. The cheapest item which I believe is 2900 Gold grants 100 AP. AP scales well to. I also don't know why people are using lethality as an excuse for ap being weak. Lethality is good on AD spellcasters which makes sense, but lethality does nothing to tanks.... AP does SIGNIFICANT damage to tanks. AP gets loads of stats. On hit, CDR, penetration, zhonyas utility. AP has never gone down or been weak. Orianna, Syndra, Brand, Annie and even AZIR do damage. AP champions need to scale to mid game. AP is still AP. They still do damage.