PLEASE Can someone explain to me these mage changes???

I read the original post from Riot about the upcoming mana change and the sentence ,,Mages should run out of mana in extended team fights,,got me.I mean like rly whats the role of mages?They are APC and should be similar to ADC ,not very mobile champions that do a lot of dmg mostly over extended period (like classic mages , , ...)not talking for champs like and . So with this nerf how will they do that, whats the point to play mage if you run out mana late game in important team fights while the ADC can be 100% more efficient than you.Riot is forcing them with this changes to be early game oriented snowball class which same as assassins(but assassins are also 100% more efficient than this than mages) SO WHAT MAGE CLASS WILL DO AFTER THE CHANGES?why would someone play scaling mage instead of ADC or AD assassins mid lane after this changes?Honestly if im forced to play and meta mid ill quit the game. EDIT:i know passive weaveclear meta with Azir and Ryze in the LCS is not heatlhy but they should only rework these champions not gut the entire class completely