The State of League of Legends

Can someone please explain to me the state that league is in. It would be wonderful if Riot would comment on this and explain what im about to talk about but I doubt it because they are never helpful at least for me plus this probably isn't a big deal anyway.

So here is what I want to understand. Before patch 7.8 I was winning games at a decent rate. Now I don't plan ranked for the simple fact I am waiting on the rune changes. I Just got into league at preseason 6 (well hit 30) and have been playing since. So I was winning more often than losing in 7.6 and 7.7 I was still winning a decent amount. I play mid lane and my of type champions are assassins. Then 7.8 rolls around and i have played roughly 30+ plus and have lost almost every single game. It is getting super frustrating because no matter how well I play I can't seem to win anymore. I am constantly getting paired with teammates who waste their abilities or feed etc. I understand everyone has bad games but its constant and when they don't do bad and im doing good it seems we still lose after one bad team fight (not even super late into the game). I understand that right now in terms of importance on the game role wise its top adc mid jungle then support or adc top mid jungle support (though I've been seeing support doing more carrying that jungle right now. Jungle is in a really bad spot but thats a different problem). Can someone please explain what changed in 7.8 that has shifted it so much because I am seeing people struggle all across the boards right now. Not just me who is unranked. I just want to understand where league is at exactly because this is getting to be super tiring and honestly not fun when I go 18/1/5 on talon and its still a one sided victory for the enemy team.

Granted I have had my bad games like recently when I played GP against zed and went 2/7/??. I did bad myself regardless of how bad my teammates did (though they also did bad)

Also before you ask (Just because it tends to come with the assassin class) I do not flame my team. I am generally silent in game though I do ping missing and danger when I know someone is about to be ganked or if my enemy laner is heading that way and I can't follow them. When my teammates complain that I need to follow my team or try to "call me out" even when I'm doing the best I can get a bit sassy. For example in one of my few GP games recently my teammates where wasting their ults constantly and they said "GP you do know you have an ult" since I hadn't been using mine. I replied with "Did you know you guys are wasting your abilities and when we need them in a actual team fight we don't have them, so I am using my smartly so that we have it when we need it or can actually get something out of it" and then muted everyone. Now I don't mind being told where I am making mistakes because that is the only way I will get better but when I am keeping them from running us over (because I was the only one doing anything to keep the towers alive) and am not dying I can get sassy when I get statements like that.

So I am just trying to understand the state of the game. It almost looks to me that Riot has basically decided that the game should be a premade team of 5 or you're just going to constantly lose no matter what or how well you do.

These are the champs i tend to play and i know they are strong right now. Also in that order. Hope someone can explain this to me instead of "you're just bad kid get good" or anything of the sort.