If you define "fun" pejoratively as trivial, fleeting, party trick, saccharin nonsense, and define "engaging" as good, honest, long term, interest, then yes, what you say is tautological true.🤷🏿♂️
But that's not what "fun" is.
I could describe "engaging" pejoratively as overly gamified, engagement focused, psychologicls tricks that play on human psychology to create long term patterns that aren't beneficial to the user, and "fun" as genuine long term motivation.