People say these types of things, but they aren't actually true. Sure, you have SOME players that are good enough to be played every day, and in a set position, but the best teams in the league will still move their players around the diamond. The Phillies do it, the Dodgers do it.
Excluding catchers, how many of their top ten position players (by games played) played 5 or more games away from their "primary" position:
Phillies - 7
Dodgers - 6
Yankees - 5 (but mainly OF swaps)
Guardians - 5
Astros - 5
Twins - 5