How to carry as a tank?

I am masters on both dps and support but plat-diamond on tank. I believe if I was playing my better roles at my tank rank I could easily carry games but for some reason tank isn't clicking for me. On dps I've mostly played venture, tracer, sombra and on supp brig, lucio, illari. On tank I mostly play doom and dva tho it does get annoying being counterpicked literally every game.

So my question is how could I apply my masters level dps and supp skills to carry as a tank in plat? Why is it so hard for me to apply my skills onto this one role?