I don't do PotD anymore but I do see its benefits for people who wants to keep the game going and who aims to level their characters quicker. I don't think removing/overhauling it would turn people's attention back to the open world content though.
I personally love doing F.A.T.E.s (some of it) but it gets kind of lonely, and my birb could only get so much exp from them. I do love the idea of improving on both these contents, especially chained F.A.T.E.s for the older areas but I don't have better ideas, just pump up the rewards or give gear I guess? I liked how I got a barding in a Churning Mist F.A.T.E. from back when.