That depends entirely on how obsessed you are towards getting the "best" gear, especially since there is no incentive beyond clearing the same content again.
You can very easily finish what the game has to offer, even if the game is a loot shooter.
Grandmaster 3 - when you clear everything at that difficulty then sure - you might be bored. But to do that will take a lot of build refinement and effort.
By then there will be further updates out.
Essentially you don't seem to want a loot shooter or buy into what one is...
This isn't like destiny. Its a more complex stats build game. It isn't a case of "oh I've got this exotic and that exotic" its constantly grinding to refine your loot in order to take on higher difficulties in order to get better loot....
That is the game. Like it or not. It's never pretended to be anything else.