I don't really know what you expect from a rifle designed in the 1800's that was mass-produced by the millions.
The rifle works well and it shoots a very capable round. It was given to mostly untrained soldiers so MOA accuracy was not required since they cannot shoot it to begin with. you cannot expect it to be as nice as a $1k+ Remington 700...
you know other rifle designs that were designed in the 1800s that are not half bad designs and blow the mosin nagant out of the water?
the Krag rifle
all were designed before 1900 and none are as crude, stiff, and poorly machined. also there were some countries that made the mosin design half passable, by paying closer attention to detail, machining to tighter tolerances and rejecting anything that didn't meet strict accuracy standards. russia and china never did any of those things so the vast majority of mosin nagants(made by those two countries) are exactly as described. there is no comparison whether you compare them to rifles made that same year or rifles designed in the same decade...
a 1943 91/30 is not anywhere near the quality as a 1943 1903A3, nor is it the same quality as a K98K, Enfield no4, a M38(swede), or type 99 Arisaka... the MN goes bang, and served nobly for the better part of a century but there is not a person alive that can fire all of those rifles side by side and say with complete objectivity that the mosin nagant design is not at the bottom of that list.