Just nerf Marksmen and not their crit items.
Please. Let's cut out the middle man here.
Yes, crit items are really good and there's two that are specifically designed for ranged champions. They could indeed cost more.
Let's let marksmen have some options with their item builds for once. Don't nerf their crit items; just nerf all marksmen. That'll solve the problem of them two-shotting people with IE after snowballing in lane. Trust me, people will play as them anyway.
Yes, lethality is really strong on most adc's whenever it's strong. Just nerf adc's. Then it'll be less strong on all of them.
Yes, on-hit items are busted by certain adc's. Just nerf them. Then on-hit items will be more balanced.
The Kog'Maw %max HP nerf was a good start. Keep 'em coming, Riot. Sooner or later, y'all will finally learn that in order to make your game more appealing marksmen across the board need to not be good at absolutely everything. Thank you.