Firstly, buff tanks. Barring that, take the true damage out of conqueror; Conqueror is a core problem to why ADCs are so bad; why play an ADC when to get their true damage(which is less reliable, by the way, since its only on crits) they have to shell out 5-6k gold when you can play a bruiser and get it for free? :/ Conqueror needs to be reworked; the true damage should be removed or greatly reduced and it should become more like old Fervor of Battle. They could even remove PTA to free up the slot.
Secondly, buff fleet footwork. Stop nerfing ADC's rune options; honestly Fleet Footwork being so horrendously bad is what makes it hard for crit ADCs who want to try and survive laning phase and scale so awful. If they were to return Fervor of Battle by replacing PTA and Conqueror with it, they could return some power to Fleet Footwork, allowing scaling ADCs a chance, if they're careful, to scale into the game while still providing early aggressor ADCs a means by which to apply pressure and do damage through early and mid. And while we're at it, change Lethal Tempo because, as a keystone, its insanely niche and you honestly give up a solid amount of both lane presence, damage, and sustain by going it over the other two options; is very much the weakest of the three options alotted to ADCs, in part because its so gated and it, again, rewards upfront burst. If they reworked it to be more like old guinsoos(ramping AS the longer you AA, better facilitating on hit ADCs such as Kog, Varus, Kai'sa, etc) instead of gating it behind a CD and making it an instant affect, it would be a more rewarding keystone to use. Especially since you can accidentally proc it.
Thirdly, return ER to its crit iteration. I have no clue why they opted for this rework on the item as I felt that the crit version of ER was the most successful they've ever had. Prior to its crit rework, no one built it. It was an extremely niche item and on the same level as Zephyr as a sort of Noob Trap item. They reworked it and it suddenly was a viable pick on multiple ADCs, providing much needed CDR, Mana, and Crit to caster based ADCs such as Lucian, Corki, Xayah, Ashe, Varus, Sivir. Furthermore, it was generally a buy that scaled well into mid game but, due to it taking up an item slot, prevented many of these caster ADCs from building a second zeal. Many of them would fall off after midgame or fall back onto their own utility to stay relevant. After they reworked it back to what it was before crit, we're honestly back to where we started. The item is extremely extremely niche and killed off the crit build path for many caster ADCs. Furthermore, the ultimate passive synerigizes better with many bruisers as opposed to ADCs, aside from Lucian, who use their ults and disengage usually.
Fourthly, make the jungle camps on the top side of the map spawn more often than the jungle camps on the bottom half. This forces the Jungler to choose between pathing badly to continually gank and four man bot or going top and farming there and putting more pressure on top and mid. Jungle pressure has a huge strangle hold on bot lane and the continual nerfs to wards does not help. Even if they didn't change jungle camp respawns, just returning sightstone to supports would be massively helpful. In the old days, if you were getting camped bot, the counter play was freeze at turret and have your support first item rush Sightstone; this gave them more health and allowed them to place defensive wards sooner and earlier. :/ Instead they turned support items and warding in general into yet another snowballing technique, when, in the past, it could have been used to decrease snowball.
Fifthly, either remove or rework Storm Razor; this item was a failure. I don't know who at Riot sat there, looked at ADCs as a class, and said,"Yes, what they want is a guaranteed crit for just standing around doing nothing. That's totally what they need." Just what. Why? This item is so easy to turn into a DPS item. Either make it an "energized" passive so it stacks up on AA's and movement and stacks up faster with RFC(I can see why this is a no go, even with a greatly reduced critical damage modifier), or change it so that with each consecutive crit, the crit damage modifier goes up. It could start at like 120%(which is 40% less than the one guaranteed crit StormRazor has right now) or even 100% and then scale up by 10% for each crit after, capping at 250%. This would make the item scale better so its less of a dead end item(as it would benefit from the additional crit chance and AS provided by zeal items and IE) while taking away a lot of the burst and rewarding steady ADC DPS.