I hate what happened to Fizz
It's really hard to talk about issues with fizz since everyone hates him so much but hear me out. I hope they can change some stuff about his rework to make him both more consistent to play with but also against.
The first issue is the visual on his ult. Fixing this alone would help make playing against fizz make more sense and be more clear, which would make playing against him a better experience. The ult has 2 distinct parts. First the fish flies out. This has a generous hitbox, but I assure you it's not glitched. Upon getting to the point you cast without hitting a champion, a circle forms. This circle is the area in which the fish will latch on to. There must be a visual indicator of this latch range upon fizz casting his ult. What happens is this: the fish "misses" and is off to the side. The circle forms and an enemy is within the circle. It latches on to them. This looks dumb because the transition in animations from fish going out to latching is so fast that it looks like the fish missed, then went sideways at the end to hit the player. If there was simply a circle indicating the fish latch range at the end of its cast, it would be far more obvious what had happened to players in this circumstance.
The next issue is his w active requiring a 2 second cook timer. This is a huge problem because of how difficult it can be to melee someone and then wait 2 seconds, THEN w active. So since his ult marks its target, fizz's only real assassination combo is to ult, q e to gap close, pop the w. This makes him very one dimensional and hit or miss. Combine this with the fact that his ult visual is misleading, he becomes super frustrating to play against. He will not try to trade in lane without his ult, since getting the w off is so difficult and takes so long that you are very all in if you go for it. All fizz does right now is throw out max range ults when both laners are full hp and if he hits he kills you and if he doesn't, he waits until next ult to do it again.
Trading without your ult as fizz is just not going to work. Against melee champions like
, they can do their whole trade combo in less than 2 seconds then try to escape the w pop with a mobility spell. Against ranged champions, if you use all your gap closers to get on them, e to wait out the 2 seconds, pop it, you are out of gap closers and are in melee range of the enemy. This means you are not "trading" you are just completely all in. If you walk out from there, you will take a couple spells and auto attacks to the back and certainly lose the trade. You're already in melee range, the only option is to ignite and keep hitting them. Which is again totally hit or miss design, there are no "I lost 50% hp and they lost 65%" trades. There is "did you kill them or did they kill you." Since again, walking out after a trade having used q and e means you are dying to whatever they throw at you
The current w 2 second rule is barely any better than the previous version which was % missing hp. Continuous sources of % missing hp leads to all sorts of problems such as assassins building like tanks, or "wtf that did way more damage than I ever thought it could" moments which are also unhealthy. It's good that is gone but what we are left with took away all sorts of depth to playing fizz. For example you could q and ult during your q to hide its animation but also cast from closer to guarantee the hit. You could e, flash while you are up, then ult, then q to dodge something ect. Any sort of combo is gone except .. max range ult.. gap close .. pop w..
This 2 second mark thing has really hurt him IMO. What might be better is to keep its old design, but instead of %missing hp, it simply does the magic damage over time like it does now. Then they could make his ult do less damage at max range, and more at minimum range. This means you can cast it close up still and it's not as rewarding as far, but still does SOMETHING. Plus since the mark mechanic would be gone, you could change the order of which abilities are used without screwing up the mark or taking too long to pop it