Fizz main here. At this point we're in a meta where everything and their grandmother is more durable than Solaire of astora juiced up on Sunny D delight.
No matter how many low elo people want to complain about Fizz being OP because "He dodged my Lux Q" When they telegraphed it so hard that there was literally a strip club style neon sign above their head saying "Press E to dodge this", the fact remains that he and other assassins are comparatively weaker now due to the increased durability stats from itemization as well as the "delayed damage" handicap that Riot slapped on em.
At this point fighter champions are doing everything assassins are supposed to do but doing it better while remaining far more durable. Even ADC's are hilariously more difficult to kill with all of the support itemization boosting shielding and healing over 9000 while even providing shields and heals built into the items.
Prime example of a day in the life of an assassin main. It's late game, You land the PERFECT fizz ulty from max range for max damage and are in range to follow up with Q>W. You activate your combo and.... You get exhausted, ADC gets a redemption, Locket and give or take a face of the mountain thrown on as you realize that you aren't about to even dent this a** hole and then proceed to get brazzer'd by a riven, or a vi, or some other "fighter" that bursts harder than you do.
God f***ing forbid that the support is a karma or janna as you'll feel like the ADC ended up with more health than before you hit them with a full rotation.
Not an ADC with a support that's going full on Oprah with the heals and shields? 1 defensive item is still always enough to completely demolish your burst allowing "fighter" champions to chase you down and counter burst you.
Entire team full on bruiser with an ADC that has their own meatwall of tanky champions that can still out damage you? Welp you can't do anything items wise and most fighters will have an equal amount of mobility/utility to chase you, so you're just kinda f***ed now.