I mean, for one, you could have done better in terms of originality. It's not as if, you know, there was a reddit post saying the exact same thing?
Now, I speak for most ADC mains: We have no problem with being countered by assassins. Now, that doesn't mean the assassin should be guaranteed to be able to kill the enemy carry in every teamfight; with good positioning, the adc should be able to stay alive most of the time(sometimes you will need to risk your life to be able to do damage).
So this also explains your other misconception. You frame ADC damage as if it's this oppressive, uncounterable, toxic aspect of gameplay. And here's where your post veers off from the topic that actually relates to real, optimal, theoretical gameplay into irrelevant hypothetical situations.
So we can talk, analyze the game in the context of a teamfight, or we can analyze it in terms of a 1v1 situation. Now, maybe that would have been relevant a few seasons ago, but it definitely isn't now, so that's not the context we should be balancing in. ADCs require extensive peel, a strong frontline along with their own mechanical capability to excel, which requires them to play with their team nearly all the time. Do you disagree?
So the job of an assassin is to find the right time to go in and, as their name suggests, assassinate the ADC. Which implies that AD carries by themselves shouldn't be able to outplay an assassin if they have allowed a window of opportunity to be engaged on by them. I agree.
As for melee champions in general, this is too broad to generalize. But I assume you are talking about champions that you complain are prone to being kited by carries. But that isn't actually their JOB. They aren't assassins; they aren't charged with hunting down a carry and killing them, but rather to either disrupt the enemy team and/or provide a sort of wall of protection for their own team. If the super-tanky Zac is able to keep the ADC busy while his team dismantles the enemy, has he not done his job? Or does he really have to kill the ADC to consider it a success? I think not. So again, we're looking at a more realistic teamfight scenario rather than a hypothetical 1v1 which would really never happen with an ADC past laning phase. These kinds of champions aren't meant to be a huge threat without another champion that provides damage.
So I don't know, melee is too broad. Give me something more specific and I will talk about that.
As for damage, yes, it is counterable. And I assume you haven't played ADC. Because, the damage of ADCs, when we're talking about autoattack damage, is countered by threat. Again, we are looking at a teamfight scenario. The threat of being caught out by CC, creates a sort of "danger zone" that an ADC must navigate around, constantly taking in information from an ongoing teamfight and knowing when they can go in and autoattack. This is why a Jhin ultimate can actually be a decent substitution for a consistently DPSing ADC, because ADCs can't always actually consistently do damage. The last season has, more than ever, emphasized positioning and threat over actual damage, which I believe is just a natural evolution of a game becoming more complex.
So I think you are not only generalizing all ADC mains with the strawman you used in your post, but you also need to look at the game from a practical standpoint. How are games of League of Legends won? What are the roles of different champions in the current meta? If you focus purely on one concept and don't apply it properly to the overall impact it has and its relation to the game , there really is no value to the concept. And such is the problem with most posts regarding balance.