I mean, I said "in that era" for a reason. The Mk 16 came into being with the full benefit of the experience of both American and British efforts to make a useful 4.5-6" DP mount, and in particular I think the weaknesses of the 5.25" on the KGVs and the 6" on the British cruisers.
Many powers designed and built large-caliber DP mounts that were ultimately too slow-loading or too ponderous to be useful against the higher performance aircraft that started appearing in the early 1940s.
That era includes the Mark 16 (It was a 1937 designed gun mount that is descended from the Mark 8 six inch bore predecessor). I do not pretend to know exactly why the US gun failed, but I do know historically that it was not considered a success and that
down to the present many other attempts to produce a high angle (or articulated) mount for large bore weapons greater than 12.5 cm in diameter have met with an equally remarkable lack of success. There are exceptions like the Borfors 12 and 16 cm mortars that are popular with armies today, but those are the exceptions to what seems to be a general mechanical rule. The handling gear fails at some critical threshold shell weight line it appears.