Why are mobile fighters tankier with less conditions than juggernauts?

And why does Urgot who outranges and out-CCs me also out-tank me?

basically depend on the enemy team being really sloppy in order to survive and have to either hunker down in one place or constantly reposition in order to activate their survival tool. Can be reduced by 40% with no effort anyway.

's healing is lifesteal-based and post-mitigation so he doesn't sustain for shit vs tanks (can also be reduced), ult armor takes ages to get to a relevant number and then vanishes as soon as it caps.

barely any in-built durability to begin with, hardly even qualifies as a champion this preseason

has to put himself to low HP to heal at all, and then hope that the entire enemy team just forgets he's there so he actually heals.

actually reduces his own durability in order to do the one thing he's built to succeed at.

is half the reason that every other sustain champ has to suffer (the other half is Soraka)

The only juggernauts who are appropriately durable these days are Urgot, Udyr and Garen; a 4k health build on Illaoi might as well be glass cannon because you'll drop just as quickly under any degree of focus fire.

Meanwhile, other tanky fighters

- Press button, get tankier. Most of it is in shields or % damage reduction which cannot be reduced by a cheap 800g or a core item for almost every AP champion (if they have sustain it's almost always in conjunction with a shield or % reduction). This is not to say that all of these champions are as tanky as a juggernaut through raw stats, but raw stats is not the only measure of tankiness.

Divers and melee skirmishers tend to have mechanics that give them artificial durability - things beyond simple defense buffs or having lots of defensive numbers. Crowd control, untargetability, mobility to avoid skillshots, etc. Juggernauts almost strictly rely on whatever durability they get from items to keep them going. With how aggressive Riot has been about nerfing tank items for the last few seasons, while compensating tanks with either buffs or "modernized" reworks, juggernauts have gotten the short end of the stick - losing several hundreds of HP and a good deal of armor, as well as old passives like OG Randuin's that made anti-kiting more reasonable. Preseason 9 only widens the gap as Overgrowth is now much worse for high HP champions later into the game, and it's not common to be short 300-400 HP in an end game. (Of course, 'end game' in chaotic preseason is usually 20 minutes, so you won't notice this until later.)

Divers more consistently and more reliably fulfill the "raid boss" melee carry playstyle that juggernauts are meant to fill into, often with less effort because they can reliably negate kiting with hard gapclosers and CC. Juggernauts being denied their rightful durability has been a design flaw that's plagued them for ages and only continues to get worse because Riot won't stop nerfing their primary source of durability - items. And instead of addressing that, when Riot does buff a juggernaut, it's almost always a buff to their damage which is, every time, completely unnecessary to make them succeed in high ELO and only further stigmatizes them as pub-stomp champions that terrorize lower ranked players.