It does not work like that in reality.
Generally, the more competitive the League the better the players and the teams are for it in the long run
All of the top sides have similar squad sizes and rotate to a small degree, but not as much as they could.
Take Real Madrid for example; you would think they would rest several players when up against lowly sides but they do not.
Lat season, for example, Caravhal, Ramos, Varane, Kroos, Benzema, Modric, Courtois, Casamero and Valverde all played over 30 league games, which, when you take in injuries and suspensions, is a fairly settled side playing the majority of games.