But not like we're "working through" a WoW update for an entire year until a new patch, right? Each tier here is significant and actually takes that much time to be done with?
Kinda. T3 is the only "big" tier, T1 and T2 are just relics of the past updates at this point. T3 will last a while just because there's nothing else to do besides that for now, since KR doesn't have T4 and we're starting late anyway. So T3 will last, but you can consider T3 as a WoW expansion. It has several patches with several gear upgrades and new raid and story content added, but eventually it'll be phased out when they release a new "expansion", which will be T4 and gear will just reset where you start doing the new MSQ, then run 2 chaos dungeon and get blue gear that's like 150-200ilvl higher than your super raid gear, and you'll have to refarm a bunch of shit(T2 gems work at 50% efficiency in T3 gear for example, so likely T3 gems will work the same in T4 gear and such).
So in a way, this is like playing at the end of BFA or Legion or Shadowlands when that releases, there's a lot of progression content to go through. There's some form of catchup, but not as clear cut as wow does usually, so you still have to progress through the previous "wow patches" instead of doing 4 world quests and getting gear that's better than what dropped at the start of the expansion. Because of this, you have several months worth of "content" to progress through. Plus our version actually has none of the "real" endgame content available and will be released over time so it'll be a true progression.
But yeah you can expect to have a year or more to spend in T3, and once you're in T3 everything you do will count towards that progression, unlike wow where they do mini gear wipes inside a given expansion, so the rush isn't particularily important.
Besides that, there's also a lot of long time grinds that improve your character on an account wide level instead, and those are arguably even more important than just the traditional gear threadmill. They offer large amounts of character power, like 40-50% increases, similar to wow borrowed power shit, only it's permanent(so far). I'm talking about stuff like getting skill potions, stats from legacy level(account level), cards and engravings. These basically carry over between tiers, and are long term investments that benefit all characters on your account while taking a long time to progress. Most of these are obtained in direct ways via quests and drops but also from long overall grinds such as Adventure tome completion(completing all objectives for every "continent"), collectibles(island hearts/giant hearts/ignea tokens/omnium stars and to a lesser extent the other stuff) and farming daily/weekly capped various content like Una quests, world bosses, coop events. All of these are interconnected and connect with other grind systems like Rapport and basically offer a lot of long term avenues to progress your account as a whole, without even actually doing raid content and such. Almost everything you do to progress something in the game will actually improve your account overall, including leveling content(obviously not everything is equal, you're not gonna get +10% dmg by farming a low lvl dungeon, but leveling content helps with adventure tome progression, which offer good rewards).
BDO had similar concepts, with stuff like setting up your empire of workers to generate ressources over time, setting up your farm, getting a cook to turn in boxes and all that so that even passively playing the game you'd make money that would let you progress your character. Although in BDO, most of the progress is via the gear, and the gear itself is a bitch to upgrade, while Lost Ark gear feels at least a little less bad to upgrade(you don't downgrade gear for example, so you don't have to gamble on your shit or have a replacement to try an upgrade, you just get mats, press the button, if it works nice, if it's doesn't well try again next day).