So let me get this straight. Morgana has been strong for one patch and she needs nerfed. Yasuo has been strong for 6 years and there are still no nerfs. Why?
Morgana mid has a ridiculous amount of counter play. You literally pick an assassin with a projectile dodge, a long range mage that power pushes, or a top laner and you obliterate her.
Who are her best matchups mid? Okay let's see:
Malzahar: Malzahar can't ult but he will shove Morgana forever and she can't leave lane to gank. He scales and she doesnt.
Leblanc: Out roams Morgana and with dematerializers can push at a comparable rate.
Annie: Still one shots people through black shield
Veigar: Literally just free farms and carries the game.
Ekko: Gets dematerializers and shoves her into tower and never interacts with her.
Fizz: If your reflexes are slightly slower than Fizz's you automatically die, but hey you can cancel the slow on his ult sometimes if you're really quick. Oh and good luck hitting Q on a trickster Fizz who has a brain.
Let's talk about her worst match ups:
Zed: You may as well go afk or spam for jungle help nonstop
Yasuo: You may as well go afk or spam for jungle help nonstop
Talon: Out pushes her and massively out roams her.
Xerath: Out pushes her, out scales her, out pokes her.
Who exactly is Morgana mid hurting? Against an evenly skilled opponent she stalemates the lane and scales slightly below average. The only thing abusable about her is having her as a "second" support late game for a hyper carry on your team. Which has more to do with team comp than it does Morgana. Subsitute Lulu mid and you have a similar situation.
Honestly, after 10 years one tricking this champion and having played every match up at least up to a platinum level I'm pretty sure Morgana is not a problem for 95% of the player base. I'm not sure if there's some ridiculous LCS or challenger shit happening right now with her, but for the majority of us players she's currently only slightly behind other mids.
By the way, Zilean mid is a higher win rate. Where are the Zilean nerfs? Oh you mean Zilean is a situational pick? Hmmmm. HMMMMMM. HMMMMMMMMMMMMMMMMMM. Sounds a lot like Morgana.