So, there were classes invented to differentiate between different types of AP damage dealers. But because of a single type of mage (battle mages: Vlad, Ryze, Swain, Ekko, Sylas) the other mages can't catch a break, let's be real, when people say "Mages are so op" they don't think of Lux, Vel'Koz. Xerath or whatever pipsqueak qualifies as a burst/artillery mage, they think of the deliquents I mentioned above. These champions need buffs, or stronger items, but because the battle mages also use those items, the community explodes when an AP item gets buffed (just look at Hashinshin)
In my opinion, the other types of mages are weak/too risky to play and win consistently with, and on top of that, these Battle Mages have every single good point you'd want in the other types of mages, and their only good point is the burst, a battle mage does more burst, hands down. So why play any mage other than battle mages?
If you've played for a while, you'll see that almost nobody wants to play Lux, Xerath, Vel'Koz or Ziggs in competitive or Solo Queue, you can't climb with those, you won't find rank 1, or any consistent challenger maining these, at some point, you hit a wall, the other players, they get good at dodging your spells, warding the places you will probably try to ambush from, and simply outscaling you. These mages rely on luck, and the element of surprise to kill others in Diamond+, and, if you're prepared, you can go in their face and crush them with almost every single champion. These champions do not become oppressive and impossible to outplay once mastered, and in the League of today, that's a problem. Another problem is the disgusting design philosophy of Riot in the last few years, TONS OF MOBILITY, every single champion needs a dash, blink, burst of movement speed, invisibility or untargetability, for whatever reason, and these mages are usually skillshot reliant, so they get hit even harder.
I'd like to see battle mages nerfed, look at this mess:
* Ryze. He has been reworked over and over, and never once did he feel fair to play against (especially for me, a puny burst/artillery mage player), and has been a highly contested pick in pro play for years. He hits you without even trying, he Es the wave, Q's a minion and damages you, he Es your ally in a teamfight, lands a Q on the frontline tank, and kills you by mistake.
* Vladimir. People have asked for nerfs for this cancer for years, a balanced champion should not make Pentakills so easily, especially 1v5, and without hitting a single skillshot. Any Vlad player is bad in my opinion, and he just abuses a busted champion.
* Sylas. How many times did Riot need to nerf this guy since launch?
* Azir. Once you get over his skill floor he shines, once you master him, he blinds everyone around. It feels oppressive, and you've seen the damage he does, with his abilities being fairly easy to land and forgiving if you miss come late game. No man should hold all this power.
And of course, the worst thing about all these champions is that they all have in common one thing, they don't need to think too hard whether they should use a spell, for most of these guys, the basic thought process is this: "Do I have mana? Is my spell off cooldown? Yes to both? Use it", their very short cooldowns, means of escape and high chance of landing spells means they don't need to worry about using a spell and getting punished, they don't have a real moment of weakness. With Lux you have to worry about missing your binding, you might try to make a pick, miss it, and end up being jumped for taking a risk (which is usually necessary, or you'd get outscaled and become useless in the late game), same with Xerath trying to use E, which also sucks when you get jumped, because your stun becomes 0.5 in melee.
I'm saying these things because I want champions like Lux. Xerath, Vel'Koz, Veigar and Morgana to become serious options in higher elo, and because these types of champions are probably the most balanced thing in the game, balanced meaning weak and unplayable.