I'm not sure I follow you, here. 4e put everything on a treadmill -- character ability mattered very little, as the spread from proficient to not was much smaller than in 5e. Meanwhile, the DCs were fixed on level, keeping the needed rolls for things the same -- and based largely on the result of the d20 because the bonus was accounted for in the level treadmill.
5e introduced a much broader range of difference between proficient and not, but the DC range is also much smaller. Remember that guidance for DCs is to set them almost entirely between 10 and 20. This ends up, by the end, of making the results very sensitive to character ability. At the beginning, it doesn't really, because the spread is so small (2).