Hi, I'm Joe. I've been playing for exactly the amount of time as Jim. Jim got lucky with forging and legendary rolls, beating my item level by 20. Jim gets to do Mythic+ dungeons I can't, simply due to better RNG. The issue is further compounded as the content he can now do offers even more of a gear advantage, which gives him access to even higher levels of content than me, both in organised and pick up groups. Since item level is officially accepted as a measure of progression and ability, RNG has dictated that Jim now performs better than me.
I've invested the exact same time as him, played just as well as him and paid the exact same subscription fee, but due to an invisible dice roll that offers wildly different results, he's progressed further.
This is bad design.