surely, candidates (f/o's) have 1. a type rating, and 2. atleast a cpl and instrument rating which requires demonstration of night competency.
agreed, line capts should not be considered, nor required to be pseudo instructors beyond the normal development of line f/o's
if otherwise competent f/o's still have landing restrictions for standard line operations to airports in the regular schedule then by definition the training is either insufficient or incomplete.