Ziggs is one of the best character designs, but....

Riot loves to protect shitty designed champions and let the good designed ones rot.

He has safe poke and safe farm. Honestly, unless the meta changes in a way that screws him, I don't think he's getting up from anything anytime soon.

He has been nerfed over and over because he was too strong in competitive where waveclear is everything. The last nerf where his Q became nearly impossible to hit did it. I think Riot said they wanted to keep his waveclear signature clear but it really hurts when it means he has to be underpowered for the majority because they don't take advantage of his waveclear like in organized team play.

His poke might be safe but it's not reliable. And in the current meta games are over before he gets to the point where he's a threat.

Ziggs and Aurelion, the two champs I love to play but never can/should.

I wouldn't say one of the best at all. Maybe somewhere in the middle.