When Lulu/Janna are picked that should be a sign you shouldn't pick an assassin
Because quite frankly, what's the point? You already know come mid and late game when team fights begin and you, the assassin, are about to engage on the adc you are gonna get cc locked, bursted down with 2 autos and the adc is gonna get a secondary life bar in the form of shields. This doesn't even take into account if they have summoners or not.
Janna and Lulu honestly make killing the enemy team's carry feel like a fucking mission, because there's no other scenario where I have to be so keen on what abilities have been used in a given time frame so I have an idea of when is the best possible time to go in to avoid the adc just getting peeled like an orange.
This wouldn't be such a big deal if the current state of the game didn't revolve so heavily on which team's adc is more fed/has more functioning brain cells (better bot wins), sadly it does.
Its honestly astonishing just how effective these 2 champions are at nullifying an entire class of champions.

who also all specifically counter assassins and divers trying to target the adc.
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Jungle
Mid
ADC