Abstraction of power, and riot's reluctance to add in negative mechanics or remove handicap mechanics.
It's not just a matter of damage creep, mobility creep, snowballing, Itemization, exc.
It's the fact that so much of the power in the game has been stuffed into the mechanics of the champions rather than the numbers, and the numerical balance gets neglected as a result. This really just comes down to, champions aren't strong or weak based on numbers, they're strong or weak based on mechanics they have at their disposal.
This ends up leading to a lot of the damage creep in the game as a result of pure mechanics not inherently being sufficiently powerful to make a champion statistically strong (e.g. bard release), even though there was no necessity to make him numerically stronger.
With itemization, it's about how many mechanics item have now, instead of just being different variations of stats. This is exactly what riot tried to shove onto mages with the hextech items. What happens is that items get powerful based more on their mechanics instead of their comparable attributes, but you can't make the mechanics insignificant. The worst offenders are probably the zeal items. 
The only difference of these items is in the mechanics which are attached to the items, and a few small stat changes, but those mechanics account for the majority of the power of the items and abstract the actual power of the items. There's no way of determining how much extra gold you'd need to spend on stats in order to have stats equivalently power to a Static Shiv, even more so when the other items also have abstract power attached to them with their own mechanics. The fact that incomplete items tend to be purely stats makes it nearly impossible to not complete one item at a time.
Some examples of lacking negative mechanics (and by extension actual decision making), is Kayn or Zoe, in that neither have mechanics which they really have to be concerned with using inappropriately. As in, if i do this, then it's going to cost me more than it will benefit me. The closest either of them have is Kayn's ult, but similar to zed's ult, it'd really only be a negative mechanic, if the kayn player wasn't in control over the exiting of his ult (i.e. he must wait 1.5 seconds before he can reactivate to leave). As for an example of a negative mechanic which does exist would be something like fiddlesticks W, which puts you at risk of being caught out of position if used inappropriately.
Refusing to remove handicaps would include things like Ekko or Yasuo. Ekko's E is just an abomination of a skill, stacked with a stun, shield, slow, and passive execute. The passive execute is what i'd describe as a handicap skill mechanic, in that an Ekko player doesn't get as punished for insufficiently playing their character, in this case, by miss calculating their burst. They just hang around for a few auto attacks... almost as if he were AD (which is why i think AD assassins either shouldn't exist or have their auto attack scaling removed outright but i digress). In Yasuo's case, he has a couple, the ult automatically playing around towers, his shield, and his E/Q combo could all be considered handicap mechanics. None of them are necessary to play the champion, they only act as a means to prevent a player from fucking up the champion too much. The shield acts as a buffer for a player who can't dodge skillshots with his E or windwall 70% of the damage in the game. His ult positioning is just outright disgusting and the most blatant example of handicaps I can come up with... His E/Q combo is just unnecessary, because every single play created by pressing E/Q could've been accomplished by simply being able to land his normal Q.
though I think even that exists because riot seems to have a misunderstanding of what makes success "skillful".
Taking things to an extreme to demonstrate my point, we can easily identify which of these theoretical vehicle mechanics are "skillful" and "experienced".
Mechanic A: Has access to all of the latest tools and a catalogue of made for purpose parts.
Mechanic B: Has a bunch of miscellaneous parts, a standard toolbox of parts, and some method of slightly altering the parts.
One demonstrates an understanding of the mechanisms and the purposes, where as the other is just parsing from a list of provided solutions.
Obviously this is more extreme than what we see in league, but riot have concluded that the opposite is true, and that having more tools with less impromptu solutions somehow represents "higher skill". This is probably why everyone who still plays this riot forsaken game for fun, would probably claim that playing Riven, Yasuo, Kayn, Camille, Thresh, Zed, Zoe, Xayah, exc, exc to a degree of success is harder than playing a "faceroll" champion to that same degree of success. Even though that "faceroll" champion, is generally going to be making due with a far smaller breadth of optimal mechanics for any given situation.
Yet when riot inevitably needs to buff the "faceroll" group of champions, the abstracted power of the other champions feels more insignificant and so they also buff those champions, and boom you've got, power/damage creep.
Sry for rant.
right now and with the current runes they make her scaling easier. There is a small tid bit of a solution however it is only a bandaid to the problem at large. That is to ban her when you can, otherwise you aren't going to have the happiest experience. You can poke her down with a poke heavy bot lane. Mainly something with point and Click. If you can get her far enough behind you can stomp over her.
Top lane is horrid. ADCs leaking into top lane. Aftershock. Riot's "listening" proposal is practically non-existent. **
