The problem isn't marksmen

The problem isn't marksmen, it's the environment they have to live in.

Stick with me here, this is why marksmen in their current iteration are well designed. The upcoming nerfs to burst damage will actually solve a lot of the problems around feeling real bad to play a marksmen, and shifting more of the ADC power away from late game to mid game is not a good idea.

1. Champion diversity - so marksmen are already making a huge comeback after the initial shake up, making their mid game more powerful has a good chance of making them 99% pick rate again because while mages and the like can all shred towers now, ADC still take the cake at shredding epic monsters like baron.

2. Strategy diversity - so one of the big complaints about the ADC nerfs has been that every game feels like a super aggressive race to get ahead and snowball through mid game. So while champion diversity has increased, strategic diversity has actually gone down. And from what I read on these forums veteran players at least have a bigger problem with a lack of strategic diversity than a lack of champ options. Kind of a one step forward two steps back kind of situation. The good thing about ADC right now is that they are super strong and viable, but because of their mid game weakness, they are not a must pick if that is not your strategy. If you let them stay weak mid game, things like Vlad an Swain for a mid game wombo combo are still really good. Heimer still a good option for heavy push n poke strats. But if you want to pick up standard tanks with strong ADC and mage back line that works too. If we take ADC from being real bad mid game and godlike late game, and push that into decent mid game and really good late game. That pretty much positions them similar to control mages no? A reduction in diversity of strategy.

3. Mid game ADC toxicity - we are in the situation we are now because there was no end of complaining about how ADC's being strong mid game was super toxic considering they were only going to become even stronger late game. So this is why we should solidify them in their role as the late game carries, we just need to figure out a way to make them not feel like hell to play for the first 80% of the game.

The solution: We want to make ADC feel better to play while maintaining both champion AND strategy diversity. So keep the upcoming burst damage nerfs, do not move ADC power from late game to mid game (as that would be the reason to pick an ADC instead of a Vlad/Swain/Heimer), and take a look at slightly toning down aggressive mobility. May be Yommuus, Predator, the new Stormraider surge, etc.

How does that solve the problem? One of the reasons ADC feel so hard to play is because 90% of what is on the map is designed to hunt and kill them. You've read plenty of posts complaining about damage and mobility creep. And this get's to the core of the issue, the real problem is that marksmen have lost agency. Their auto attack uptime has gone way down over the last several seasons. You have to dance back and forth for the first 30% of a fight or more to wait out abilities before you are safe enough to walk up and auto.

We need to reinstate a system where ADC can orb walk through the vast majority of a team fight or skirmish. The sustained step auto step auto pattern needs to be a thing again. Push up auto attack uptime from like 60% of a fight to like 80%. And if you don't boost their mid game damage, it doesn't feel toxic to let them auto a lot because they aren't autoing that hard until late game.

TLDR - keep ADC late game oriented, but allow them to navigate mid game fights better despite mediocre damage output. They will feel better to play without feeling horrible to play against since they won't be chunking until late game.