There's issues, as we all know, whatever way you go. The comparisons I was making were against before the League Cup went back to an initial group stage.
Recently
Premiership 38 league games, at least one League Cup game (previously) and at least one Scottish Cup game - total at least 40.
16 team league
30 league games, at least six League Cup games and at least one Scottish Cup game - total of at least 37 (so a drop of only three games, but as you say less quality, however, at least more variety).
Recently
In terms of home games 18-20 league games, possibly no home cup games - total of at least 18.
16 team league
15 home league games, three home League Cup games - total of at least 18 (so 0-2 less home games, but as you say less quality, however, at least more variety).
To avoid more "meaningless mid-table" games you'd have more relegation/promotion places and promotion play-offs with entries just from the same division.
Additionally there are also a lot of countries (and UEFA) who think 20 in a league is too many, because 38 league games are too many, so then you would be looking at a 18 team league playing just 34 league games (17 home league games).
Anyway, 16 team leagues is just how I'd go after listening to the discussions over the years...