@Morello about how you described fizz in the preview

Fizz is able to pressure high-value targets like an assassin, but makes frequent use of evasive abilities and favors sustained damage over burst. This creates a different sort of hit-and-run gameplay style that allows this little amphibian to dance around the battlefield, using evasion to stay alive and keep the opponent guessing.

This is the specific line I want to focus on. Quite frankly riot failed in making him in making him a sustain damage over burst champ. So much of hits kit's power budget damage wise is in his playful/trickster to the point of being it is his main part of his assassination rotation followed by hourglass active then escape if the enemy doesn't have CC/burst to use on you. Many times you are simply a hard engage suicide bomber, with your E simply delaying your death while your team follows up with your hopefully useful self sacrifice. The only way he has found success as a sustain damage fighter is through mimicking ekko's tank build.

Now there is nobody that can give the logical excuse "well he has more cdr options now". CDR has always been extremely core on fizz to function as an assassin that he has always looked to max it through items anyways. But he isn't getting the zed special of love tap nerf for inexperienced players but with bonus buff for experienced players. I assume you are looking to move fizz away from his ekko like viability of building full tank also. I think there is a big issue of what this blanket nerf to the cooldown will do to his first clear in the jungle. His passive damage reduction is completely useless in protecting him early damage to the point that the first clear is just barely surviving the first 3 camps, in lane you just accept that you will be put behind in cs early.

Now it is easy to see the OP issues about playful/trickster. It is his engage/escape/AoE farm/main damage budget/sole defensive form of survival. spreading some of that into the other parts of his kit would be the best pairing with nerfing is bread and butter ability, and enemies most glaring annoyance from fizz.