They need to tone things down as a whole tbh. The disparity of defense and offense between depending on build is too significant, and damage is too high in the later stages of the game, while defenses are too strong in the mid game. Close to 90% of an ADC's late game damage comes from items; potentially more, depending on the target's armor. Similarly, 80% of a tank's EHP can come from items, though that's before penetration. This means a tank can have as much as ~10 times the EHP of a squishy, but they do close to 1/10 the damage. It's silly for the disparity be THAT large, and with damage as a whole being as high as it is right now, it means nobody can live for very long.
Lowering item values and removing some of the multiplicative scaling from damage would go a long way towards helping to balance the game, though Crit is basically impossible to remove with Yasuo in the game (They should have just taken it out with dodge, IMO; they both caused the same issues of RNG determining fight outcomes in the early-mid stages of the game).
I'd love to see damage toned down by a reasonable amount across the board, but they'd have to rebalance everything to account for it, since lower damage means high damage melee/short ranged characters become relatively stronger. The up side to it is that players 1-shotting each other wouldn't happen as much, which means more time to make plays and respond to things.