Late game teamifghts averagely last 5 seconds, that's the problem.
and that's why league is dying, becoming anti fun. melee champs who aren't cc bots become useless, and its decided by whoever marksmen/mages clusterfuck oneshot each other first.
Edit: do you guys want to know what started this whole mess a couple of seasons ago? Say thanks to the new masteries, especially Thunderlords. Previously, you would get a slight increase in damage If you dealt a lot of damage overall, but with the introduction of thinderlords (especially when it was overpowered) it got to a whole new level. Every user got an undeserved damage chunk of burst damage output that could win Lane, trades and sometimes even teamfights. Some chimps can even trigger it with only 2 ( and even 1) without auto attacking. (looking at you Ekko, Diana, Syndra and anyone with 2 or more instances of damage in a single spell)
Quite a few examples of the consequences; -Literally everyone took thunderlords upon its release, and those who didn't, suffered the consequences. -it gave mages even more burst to kill squishies. -it gave assassins even more burst and made them even harder to counter -it made top lane bullies like Riven and Renekton unbeatable in lane -it made early game junglers especially Lee Sin and Nidalee even a stronger pick, and boosted their total amount of successful ganks -it made even pure dps marksman like Vayne and Kog take it and improve their "bad early game" -also boosted bot lane bullies like my homie Lucian. Even tanks used it, until it has been nerfed a bit and grasp has been buffed to stupidity level.

AA + Passive +
= Domination