Garen is Absurd

First off, this is a qq thread so no need to point it out, second I realize how the game works so I don't think i'm missing any drastic mechanics with dealing with Garen. Garen is the epitome of a brainless champion: Point and click spells, unkillable, silence/speedboost. My problem with Garen is not his abilities per say, but his general concept of building flat tank items and dealing more damage to your team than your own adc. I just simply can't grasp the concept of what riot was thinking giving him true damage on his abilities and a full true damage ultimate to the Villian. Every game I see a Garen they just sit in river and spam taunts at your team 1 v 5 because they know you cant hope to kill them and any damage they take will be restored in roughly 10 seconds. In my last game their Garen had full tank items plus a single offensive item (black cleaver). By 35 minutes he was true damage ulting me for 1085 true damage, SERIOUSLY? Not to mention he virtually can't be kited especially if he bothers to even group with his team. I just dont understand why riot would do this to us poor players. So anyone bothering to read this, tell me some way to deal with this monstrosity because im frankly at a loss. And before you ask I build last whisper and youmuu's on most of my adc's and assassins but it's just like i'm trying to cut stone with a spoon. If you want to kill him he demands your entire team's attention, meanwhile their team cleans up or pushes a lane. This champion is extremely irritating to deal with and has a learning curve the size of a peanut. Saying to kite him isn't feasible in 70% of the situations I encounter him and riot's implementation of these ridiculous bruiser/tank carry items makes matters much worse. Not to mention he doesn't have to manage anything but his 6 seconds cooldowns and his 35 seconds ult cd.