The amount of "tankyness" a player gets to be seems to dependent on their enemies state

Assuming I play well on a fighter I only get to be as durable as the enemy allows me to be.

Regardless of how I itemize, my durability depends way more on if my opponent is having a good game.

Enemies from other lanes who get fed can destroy a similarly fed tank because offense outscales defense.

It doesn't feel good to have the "Tank" fantasy conditional on the performance of the guy hitting you and out of your hands.