The reason Zed is healthy and will always be kept viable by Riot (their favourite AD Assassin)
From all the AD assassins, Zed has the most AVOIDABLE damage and the most DELAYED damage. Sidestep his shurikens, he deals no burst. He ults you? Try to disengage and reduce his uptime on you, he deals no lethal Death Mark damage. In team fights, this becomes even more relevant, carry gets ulted by Zed? Shields, CC, Heals all can stop him from doing anything, because the damage is DELAYED. These are all counterplay based on you, your skills and your abilities. Now, there is also counterplay with items: Zhonya, QSS, Mercurial. These items reduce the Assassination potential of Zed drastically.
This is the reason Zed has his safety, because his damage is not reliable, if he didn’t have his safety, he would be garbage. Every other Assassin would be better than him, because they do have RELIABLE INSTANT DAMAGE.
Whenever other AD assassins became really good, (rengar recently, Kha’Zix and Talon season 3) they were instantly nerfed, because they truly had no counterplay, point and click RELIABLE instant damage.
The QQ about Zed has been going for years, yet riot always keeps Zed relatively viable, because his kit is inherently the most fair for the enemy out of all the AD assassins, it offers the most counterplay. This is where the risk from Zed comes in, picking Zed is a risk in its self for your team. You have to get fed and you have to be BETTER than your opponent ALL THE TIME. There are games when I am 8/1 Zed and I fail to kill a squishy because I miss my double shuriken or he does a nice sidestep. This would never be the case with a Talon, even with a score of 4/1, I jump, hit all my abilities because they are reliable and 1 shot the squishy. Same for other Assassins with reliable damage.
This is why Zed is riots favourite AD Assassin and why they call him healthy, pair that up with a very high skill celing kit and potential for flashy outplays and you should know that no matter how much people cry about Zed, he will always be relatively good and viable. I suspect Riot is trying to force a comeback for Zed in LCS with the nerfs to
(the reason Zed stopped getting picked in LCS) and their experimentation with new AD assassin item
and the "future ad Assassin items" they have planned.
So if you hate Zed, the best thing you can do is play him yourself, understand his kit and then beat him with your better understanding of the champion. QQ'ing on boards will get you nowhere, Zed will never be gutted and removed from viability like some other 1 dimensional champions with very little counterplay in their kit have been gutted in the past.
Zed in the midlane is what Lee Sin is in the jungle, you will always see those champions.

since he is even easier to avoid and doesn't 100-0% as Zed does.
. Is his burst great? Yes. Reliable? Yeah, kinda. Front-loaded? Yes. But he has no real escape. Beyond lane, all he can do is blink, kill, die. And it leaves him with a 1-for-1 trade if he doesn't make any escapes. His passive is almost useless, and his E is just a dash and some dump buffs. Zed is everything Talon is, but better, with an oppressive lane and with late-game use as a splitpusher
- while his damage is NOT magical
- while you need mana regen