I don't think the 44 mag is inherently inaccurate. I think the problem is manufacturing tolerances in revolvers and the way they've carried over to rifles. And the twist rates--let's not forget about the twist rates.
I used to think the 45 Colt had rather lack-luster accuracy. I'd owned 7-8 of them, none of which were particularly accurate with any load I could find. Then I got my hands on a Linebaugh conversion built on a 44 Super Blackhawk. Tight chambers, cylinder throats +.001" over bore diameter, and all the same. A near-perfect forcing cone. With hot-loaded 456191s, it was the most-accurate long-range revolver I'd owned to that point. The same tight chambering, and a ball seat to the same diameter as the cylinder throats, gave equal accuracy in a re-barreled M94 Winchester.
There's no reason the same thing couldn't be done with a 44 mag, if someone was inclined to put the money into the project. Set up a single-shot with a 1:20 barrel, tight chamber, and go from there.