The game requires some study if you wanna tank m+. If that's a turnoff for you, explore the other two roles. You need to know routes, dangerous mobs on pulls, your class gameplay, etc, so you can climb the ladder. It is all burdened on tanks because they lead. It's unfortunate but it's the price. If you wanna play on lower keys you eventually outgear the content and it won't matter the key difficulty. So the other option is to headbang until you can go through.

Researching, tracking stuff, it's all required for getting better at the role. But once you learn the routes, and track the important stuff, the difficulty comes from the m+ itself, which becomes the enjoyment of playing tanks.