Removing Critical Strike would fix a majority of the problems regarding Marksmen

Critical strike chance has always caused this weird fluctuation between ADCs being incredibly weak until hitting their late game spike (which causes late game ADCs to have high winrates usually) or they're completely too broken as they damage well early and can still do their crit hyperscaling (which causes early game ADCs to have high winrates usually). Riot has always been enforcing a meta of ADCs building crit. Building armor pen? Nerfed that dead. Building rageblade? Nerfed dead. They refused to try to balance it. Just kill it off and force them into building Crit.

AD carries just have too little itemization options and are forced into things. They always have 2-3 crit items, 1 being IE, a lifesteal item (pick of 4), and a last whisper item. Mages build completely independent based on their champion. Swain and Aurelion build a tanky DPS mage. Annie builds an assassin mage. Viktor and TF build Lich assassin mage. Mages only have 2 items they're forced into: Deathcap and Void Staff. Bruisers have the requrements of 1-2 damage items (being Cleaver/Trinity, Ether Hydra, and BoRK) into unlimited tank options. Tanks just go Sunfire into the umlimited tank options plus Visage. But again, AD carries have to build the same thing: IE, Zeal, Zeal/ER, BT/BoRK, LW.

Image the build diversity if critical strike was removed. Miss Fortune would build armor pen to be an carrykiller who's main goal in fights is to get off the perfect ult. Lucian would be a spellweaver that does moderate damage to tanks but can still hurt them a bit while being a lane bully by building Trinity. Ezreal would probably lose Sheen interaction as new AD carry items would make him too powerful. Vayne wouldn't Q one shot and would be forced to be a tank shredder. Of course some champions would need adjustments. What should happen is:

Berserker Grieves are nerfed, so Lucidity Boots can compete with them.

Infinity Edge changes and gets a passive that increases Auto Attack damage by 25% (except onhit effects). (Would apply to champion ability onhits like Yasuo's Q, GP's Q, Ezreal, Q, Cait's passive, ect, but not Kayle's E or Yi's E.)

Ezreal's Q would no longer apply Sheen effects because of the above and below.

Essence Reaver would change into an item that grants 60 AD, 20% CDR, some mana, and missing mana regen. Buildpath would so change into BF Sword + (New Item that builds from 2 longswords + Sapphire Crystal. Grants lesser mana regen than ER and gives 10% CDR).

Yasuo's Q AD ratio is increased. Riot can go balance the rest of his kit from there.

Lucian's base AD would increase, but his ability damage would decrease a bit (helps with Trinity builds).

Rageblade would be reverted to what it was preseason 6, but keep the same build path. (Also attack speed onhit would be changes to 6% from 8% so it wouldn't give ~80% attack speed.)

There would be a new attack speed item that gives 70% attack speed and has a passive that applies onhit effects an additional time every 3rd hit. This item would also work on AD champions like Rageblade which is mostly hybrid. (Similar to today's rageblade, but it doesn't have stacking and isn't every 2nd hit.)

Hurricane would lose it's crit and just gain a bit more attack speed. Also the ratio on bolts would increase from 25% to 35% as it no longer crits. Also no longer builds out of Zeal.

Stattik Shiv's passive's chaining range would be doubled and gets to shock 1 more target. Also the passive gets a 40% bonus AS ratio (since it can't crit anymore).

Zeal is changed into building out of Dagger + Longsword for 1150 gold cost. It gives 15 AD, 15% attack speed, 5% movement speed, and now gives some onhit percent health physical damage. Every item that builds out of Zeal (except Hurricane since it doesn't build from it anymore) would enherit the percent health damage passive.

The reason behind the percent health damage idea is if tanks are killing in 7 attacks by a marksmen who crits, and meanwhile that same marksmen kills other marksmen in 3 hits from crits. However if they deal percent health damage (for some part), they would still kill the tank in 7 attacks, but they would kill the opposing marksmen in 5-7 as well. (Number of attacks is an arbitrary guess.) This would make Marksmen sources of DPS to kill tanks (mostly) while not quickly killing other marksmen (mostly). This would also make marksmen who build most armor pen (or this this scenario, not percent health damage) deal less to tanks as they wouldn't have crit to fall back onto.