The creep nobody talks about: Defensive Creep.
When people talk about creep, it's always the same topics: Damage creep. Complexity creep. Mobility creep. etc etc etc. Same topics, tired and true. What nobody talks about, however, is defensive creep.
"BUT TANKS ARE IN THE WORST SPOT THEY'VE-"
Cut it out. Tanks are not nearly as bad as boards makes them out to be. Especially not in pro play, where coordination is highest. That said, "defensive creep" isn't just self preservation but also ally preservation.
#Defensive Creep on solo-characters.
Straight-up: Defensive items are better now than they've ever been. "BUT TAN-" No. Not tanks. Everyone. Mages have access to better protective items than they've ever had without having to dip too far outside of their pool. Things like Protobelt, Abyssal Mask and Seraphs are all better at keeping mages alive, not to mention Aftershock letting them tank absurd amounts of damage while going ham. Tanks can dip heavily into early game itemization that benefits in the long run rather than just falling off and tanks in general have more HP now more than ever. Fighters still get great items like Steraks (more on that) or self-sustain (More on that too.)
Most characters also have access to some sort of buyable shield regardless of position, from PD to Steraks to Maw. If shields aren't your thing, you also have access to a bevy of sustain choices like Death's Dance, Ravenous Hunter, Overheal and all sorts of potions and trinkets ill-gotten from Klepto. With mana regen being higher (which is better for tanks and low-mana classes more than mages), you're more liable to spam spells and benefit from healing abilities.
And of course we have characters and champions. Champions with massive amounts of defensive abilities on low CDs like Irelia and Fiora. Sion, who single-handedly raised the bar for what it means to be a tank. Champions like Xin Zhao getting reworked to block more damage than they ever could. More spammable heals, shields and defensive cooldowns. It's telling when Vi, one of the most offensive-minded divers in the game, had her defenses buffed over her offenses.
But they're not the main offenders.
#Defensive Creep on Supportive Characters
Back in the day, the most protective character you could get is Janna. A champion who literally invalidated melee characters. Alternatively, Shen: An ultimate with a massive cooldown that will summon your very own personal Shenpai ninja body guard along with a big, fat, disgusting shield.
These days, those characters are often long forgotten by the two biggest criminals in the tanking world: Braum and Tahm Kench.
Braum is literally the ideal tank, creating a massive barrier between your squishies and your enemies. He can eat skillshots and projectiles with his W on a moving body that can stick to a target, far better than the oft complained about Yasuo, while providing self-damage reduction when you do hit that shield. Braum's concussive blows also make it hell for anyone who does get close. He has peel just a bit shorter than Janna's while having the benefit of being massively tanky. It's extremely telling that the only champion who could top Braum in terms of pure defensive utility is...
Tahm. Fuckin'. Kench. The king of invalidating plays. The utter bane of existence. A champion who can utterly negate a pick, CC or otherwise. A champion whose existence is a get out of free card against pick comps. This champion was the only thing that could top Braum's 24/7 bodyguard play by being the ultimate in "protect this idiot" technology. He's a champion like Soraka: A pick that makes others hate the game because they didn't play around the eight second cooldown. Windwall you can bait out and force on a 20-something CD. You can't exactly play around Tahm eating your enemy unless you have a DOT.
This, of course, doesn't account for the mass of supportive itemization buffs. Knights Vow. Athene's Grail. Redemption. Iron Solari. Mikael's. Don't think I haven't forgotten about items that lower active item CD that make these items even more common. Not to mention the support item changes which give supports more sustain in lane and more ways to remain in lane to further buff their adc. The fact is that it has never been easier to keep a subpar player alive if you know what you're doing because of just how many ways there are to keep them out of the fire.
Shoutout to Runes too. I see you over there.
#Why it matters
One of the things I've come to find about being a QA tester is that the root cause is what you want to find more than anything. Everyone likes to complain about damage but nobody complains about durability or ally protection. Besides the obvious answer of "Because boards greatly favors tanks and supportive characters" (Hell, Braum was the #1 most popular champion in a survey done on Reddit between EVERY SINGLE LEAGUE CHAMPION back in 2016 or so), the reasoning is that defensive creep is much more subtle than any sort of other creep.
Everyone will call out when a champion has 2-3 dashes. Nobody says anything when honeyfruit can keep a champ going with lane priority. Everyone will call out when a champ has %HP True damage on a random timer. Nobody says anything about them being able to parry all damage for a second at a consistent, fixed rate. Everyone will call out when damage is too high. Nobody says anything when this damage was a direct response to prior metas.
It's telling that the Season just before "THE DAMAGE CREEP" hit full swing we had an incredibly play-it-safe meta of protective supports healing and buffing the shit out of ADCs, leading to deathball comps. Even now, in the "biggest damage creep wave ever", you're more liable to see a champion like Urgot (Tanky DPS), Aatrox (Big healing slobberknocker of a champ) or Sion (What you find when you google "Meatwall") than a pure high damage champion like Zed or Yasuo.
But most of all: Ignoring it won't fix anything. If you nerf damage and defense stays the same, you end up with the same situation: Giant long-ass games with zero skill involved of champions trading simplistic trade patterns with no real repercussion. Then you lead to Riot having to buff damage to deal with this insane durability. Then the cycle repeats over and over. If you really want to see change, cut down on protective items and nerf supports who can babysit champions. Give real drawbacks to an ADC being out of position rather than having a Rakan charm, dump redemption on them and then chain-CC while a quarter of the damage you deal goes to him.
Defense needs to be looked at because otherwise we'll just dip back in Season 7, then back to Season 8, and over and over til the heat death of the universe.
beats
But loses to
Every.
Single.
Game.
Had.
The.
Same.
Champions. 
Not to mention in the class reworks of season 6 & 7, tanky items across the board got nerfed, and have stayed that way since. Defencive creep has been skewed to favor offensive champions.