Part of the reason damage creep is up is because of the culture of nerfs
When I say the culture of nerfs, I mean how the community reacts to nerfs.
Most of the nerfs in this game are what i like to call 'ghost nerfs'. They are nerfs that change extremely little or any at all, but the community SEES this, thinks 'nerf' and automatically assumes its not as strong.
While its not AS strong, its still going to be JUST as effective.
When I see electrocute nerfs for 20 damage and 10% BAD, or 30 base damage max rank Talon W nerf, these are not nerfs. You could still use these things and nothing is REALLY going to change. The only change this would literally ever be relevant in, is if the target ended up living with that much hp left. Which usually they dont. OOOO watch out guys, Irelia's Q got nerfed by 5 damage. This doesn't mean anything.
This becomes a placebo effect, You see nerf, you assumed it was good, and then it wasnt as good. But when you dont pay attention to it, the damage is still there but since you saw the nerf youve adapted to it and assumed it was fine.
This stacks up over many many patches and youre left sitting wondering how the fuck damage is so high.
You could say "But the winrates change, so it has to mean its working" Well then you have the Vladimir effect.
You see, there was once a patch where vladimir was strong, and received nerfs. In that patch, his winrate went down, by a lot. But it wasnt until the NEXT patch that it was revealed the stat changes accidentally didnt go live. But people assumed they did.
So it proved that nerfs are largely received MOSTLY in the mind rather than the actual game. Just because winrate dropped, doesnt mean anything. I remember back in season 3, kennen saw a .003 AD nerf and lost like 4% winrate.
THIS is how damage got to this point.