I said this when runes came out and I still think I'm right.
There is no mid or late game it's just insta burst all game and it will continue to be an utter circus until you give every champion back the resistances they lost from seals and glyphs. The game was balanced around these base defensives since they were virtually universal. Not taking them was considered greedy. Removing them has obviously caused a problem.
Kog'maw was never broken. But you took 12 mr from glyphs. Now the champion with %hp magic damage on each auto is suddenly broken. Kog'maw didn't get stronger. No one got stronger. Everyone else just got weaker and some were able to abuse it more than others.
My other example is my midlane main. TF lost 9 armor and 12 mr from defensives, and was compensated with... 13 max hp.
Kind of surprised the balance team couldn't foresee this and still hasn't identified this as the main problem.
And then they released Zoe.
From a broader perspective: You legit had to win MORE THAN ONE TRADE before you would consider all-inning for a kill. It required consistent outplay. Not someone making a solitary mistake and losing their tower at 8 minutes. You had to play around the champ and the players tendencies (Champions just feel all homogenized now as a result but that's a separate issue) and the game doesn't have that feel anymore. It more feels like 'Just wait for them to screw up'. The game doesn't reward proactive play. Everyone plays risk averse. LCS is boring af to watch compared to past seasons. I see Gnar v GP lanes in my sleep. I don't feel like I've been outplayed when Tristana crits me 3 times and I die. I don't feel outplayed when Zoe pops me for 80% of my health with a lost chapter. I don't feel outplayed when support brand gets a liandrys presses E and walks away and burns me for 1/3 of my hp. I don't feel outplayed when a full tank J4 claps me in 2 seconds.
I certainly don't feel outplayed when one of my laners falls so far behind you just watch map pressure slowly die off until you get starved out. I don't like my other lanes snowballing so hard I feel I had no control over the game at all even though I won. It doesn't feel nice when falling behind is not 'I gotta farm back up and play safe' but has become a perpetual death sentence to be perpetually behind the curve until the games over.
It's not fun when your options become 'We either lose or just hope they throw hard.'
And this is ultimately all the result of one thing.
-9 armor. - 12 MR.