Real talk, I think people just got way worse at league and its Riots fault.
I've played this game on and off since like.. season 2.. though up until season 5 I played mostly TT. I then got sick of League, stopped playing for half a year, then started playing a few games a week on and off with some breaks since S6.
For the last 4-5 years playing on and off in both ranked, and norms.. I've noticed things. While the damage creep and abysmal season focus's are a big thing.. I honestly think people just legit got far worse at league in general..
This isn't entirely their fault though.. Riot is to blame, and their constant push on meta's. Their toxic and abhorrently disgustingly inept design of the macro game in general (something I doubt they even think about anymore), and the feeling of hopelessness they have injected into the losing team with insanely overloaded snowball mechanics.
Back in Season 4-5 for example, I was bad. I was used to TT, and playing SR for the first real time was a big switch. Needless to say I over extended ALOT in lanes, I pushed too aggressively, I wasn't used to such a big map, and the laning phases are way different than they were in TT...
I'd often come to the forums, or people in chat.. and what would they say? Even in bronze, silver, and gold. "Don't over extend.. if you're behind let them push CS" yada yada.. These basic fundamentals of wave control, and tower hugging became something even bronze players would do and know to do.
The biggest problem back in the day was mostly just knowing how to close a game and push an advantage... Now in this season, what do we see? constatn wave pushing, virtually no lane wave control, mosh pit fights, and scrappy fights literally everywhere, and even in PRO play which NA was so gracious to show us.. the gameplay and macro meta of the game is so abysmal even Pro's are defaulting to aram in SR..
So what happened?
Riot kept messing with towers.. making them weaker and weaker, while adding more and more ways to knock them over faster, and tank them easier.. "hug turret" became something that didn't seem plausible anymore.. So you HAD to push lanes.. You couldn't just sit back anymore.. Granted, this isn't entirely true, but.. with that meta shift, and constant tower dives at level 4 with no way to get out, made it feel like towers are useless.
Then they added the god forsaken gold injections into the towers with their plates.. creating an even more snowbally "better push your lane to get those plates" mentality in the players, throwing wave management out the window even more.. why would you want to freeze lane when you got potentially hundreds of free potential gold right behind the enemy?
Now add in the constant buffs and iterations to the epic monsters, drakes, dragons, and baron changes through the year, having control of the lanes, and pushing your opponents became even more pressing and important. Better not freeze bot lane, that means we have no drake priority, gotta keep push push push.
Then they kept going with the damage creep, more and more damage with more and more overloaded champs... why freeze lane, have wave management, when you got a tool in your hands that could kill your opponent giving you free wave push AND free gold in the plates?
Why learn any of the micro/macro skills when all I gotta do is face roll my keyboard and maybe get fed and win with an overloaded champ?
And therein lies the problem.. It's the same mentality of power corrupts, and power blinds. You give people such overloaded champs that have such insane damage, they think they can "outplay" their opponent, and.. 1 of them does get outplayed. Now you got an overloaded champ steamrolling everything, and screw wave clear, wave management, playing safe, and well... playing intelligently at all...
None of it matters anymore, which is why none of it is done anymore.. even in plat so I hear from plat players and friends that wave management, and many of the micro/macro knowledge and skills of old are all but in the past and forgotten.
That's half the problem. While damage creep is bad.. its the players faults that its happening at 10 minute games are a thing, but its Riots fault for pushing such an abysmal macro game and meta that pushes all of that out, or makes it feel pointless to begin with while hanging carrots like plates in front of the player enticing them to make bad decisions for a potential huge payout...
Now you have newer and newer generation of players starting to play league, while the others start quitting, and you're now replacing the knowledgeable players with players who have no clue wtf to do besides beat their face against the brick wall in hopes it'll fall, and if not blame someone else, because wave management, and playing safe is something alien to them, and none of the current gameplay mechanics entices, teaches, or rewards for playing safe, being safe, and playing smart.
Why aren't there rewards for playing smart? Why aren't there rewards for being both aggressive, and rewards for playing safe? Not giving up x amount of kills by x time rewarded with stronger tower defenses? Or better mountain drake bonus's, etc.
The macro of league is non existent, its just "get a kill, auto win lane, stomp the game" and nothing in between.