According to Pro Football Focus in their QB Annual, Dak ranked 21st out of 35 QB in 2018 with 48.6% of his aimed attempts that were considered "accurate." It's important to note that PFF doesn't consider all catchable passes "accurate," but only those on which the receiver didn't have to extend his arms outside what they call the "frame" (the zone of his head and torso) to catch. If the receiver bent down, reached above the top of the helmet, or to either side out away from his body, they called that an "inaccurate catchable" pass. Any catchable pass that isn't caught is considered a drop by PFF, so there is a weird grey area there that includes so-called "inaccurate" passes that should be caught.
That distinction between "accurate" and "catchable" means a lot, because PFF ranked Prescott 9th out of 35 with 68.0% of his aimed attempts that were considered "catchable." So I guess you could either say Dak ranks in the bottom 15 (out of 35) or in the top 10, depending on what you think accuracy means. PFF's George Chahrouri, who put the QB annual together, says "It's nice to throw accurate passes, but it's terrible to throw uncatchable passes."
Whatever you think about PFF's terminology, they did watch every pass of all 35 QB, so this is probably as thorough an analysis and as objective a ranking as you're going to get without watching every pass of every QB yourself.