i'm there with you. i haven't touched the game since january and i don't plan on touching it for the rest of sl. i did seem the misunderstand what you were trying to get across. legion does share similarities with bfa and sl but i'd still say that legion is quite different. with artifacts, you didn't have to regrind AP each tier to reuse the traits though you did have to grind each weapon. probably the biggest difference is the class design. legion artifacts were made around how the spec played. so as you progressed your artifact, the spec felt more and more complete. this eventually led to the incomplete shells people experienced at the end when the traits were taken away. then bfa tried to replace customized artifacts for each spec with generic traits with azerite gear.
you could certainly make a comparison between legion and bfa/sl but i'd argue that bfa and sl are just poorly designed versions of legion. though legion does still hold hate with me for destroying ranged survival and giving us a clunky mess of random abilities to replace it...