Why Karthus is left to Rot

I don't understand. Anivia's kit is literally a shit ton of AoEs and CC that enable her for high single target burst and AoE damage and she even has a passive that helps her if she fucks up. She gets a second life with no cost to her HP pool. Karthus has a similar HP pool (like 10 or so difference) for a passive that essentially requires him to die to get value out of it and even then there are so many ways to counter it and doesn't even allow used of summoner's or actives. Anivia's rework if anything removed her weakness of her early game, which was if you could out run the Qs you could win lane. She even has a better wall.

Now she can at lvl 14 with the same AP as Karthus do 1k damage in a single rotation to Karthus's 500 because she isn't ever going to be in range of his E. And to top it off, Karthus's is a skill shot that people can walk out of the center with about 330 MS and she has 335.

Like I don't think eating someone should save them from a global on target ult but at the same time let people like continue their ult inside of him. I call new champ favoritism on that. And his ult is on almost as long of a CD as Ignite. It really should start at 180 and go to 120. 200 is really high when ignite is 210. Even with 40% CDR that ult is only up every 72s. And Karthus has no room for 40% CDR with his kit. He is basically locked into buying just to make up for how immobile he is and how squishy he is.

Karthus need's to be able to cast while moving on Q. No more cast times will help a lot. And it really needs to be on a .4s explosion time instead of .5s or up the AoE from 100 to 125.

Another thing. His E really needs buffs to mana cost since mana is so much harder to come by now. 30 / 42 / 54 / 66 / 78 for a non ultimate over time is ridiculous when it shuts off the passive. It should be like 30/38/46/52/60 and you get half effect of the passive. 60 per second with Q is over 100 mana per second usage meaning maybe a 16s total uptime at most for Karthus after the buffs if he lives that long.

That is literally all I think Karthus needs to even be able to compare with Anivia in to why you would take him. His trade off would be global utility over team fight utility. And he would have move counters availabe ( and more).

Karthus may have a 50% win rate, but it doesn't really mean anything when I look and see his play rate is abyssmal and he is only picked as a super niche pick and still very rarely. I feel like just looking at his Diamond Ranked he is only played by like 1 guy. And Master+ it's even worse. http://www.lolking.net/champions/karthus?chartType=winrate&region=na&map=sr&queue=1x1&league=diamond#statistics The loyalty is also less than 1% for over 50 games on him in Plat+.

That shows just how bad of a state his kit is in. When there isn't even 1 person making him work or even maining him in high elos.