The teenager, viewed as one of the brightest young prospects with the English champions, replaced Diego Costa before halftime but was substituted himself half an hour later.
"He has to learn that at 19 you have to run three times as much as the other guys," Mourinho told a news conference.
"You have to play in your limits and you don't have to play like a superstar with the ball at your feet because this is not the under-18s.
"I don't accept that a player ... when we don't have the ball, doesn't press, he doesn't have intensity and he is waiting for other people to recover the ball," added Mourinho following Chelsea's final match of the season.
"I don't accept that in superstars and I don't accept that in a 19-year-old kid. He has to learn what it takes to play for us."
Loftus-Cheek has been brought into the first-team squad this season but made only sporadic appearances for the Londoners.
Earlier this year the Portuguese said that he expected the teenager to play a more prominent role next term.
(Additional reporting by Douglas Beattie, editing by Tony Jimenez)
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