That something is "enjoyable" in the short-term does not mean that it is beneficial in the long term.
Doing drugs, getting high, gambling, any other short-term dopamine hit is easy, and feels good in the moment, yet can pretty easily be characterized as bad in the long term, and objectively worse than alternative actions that in the short term are not as pleasurable and enjoyable. I use obviously extreme examples to illustrate the logic.
Figuring out which pursuits and behaviors fit into which bucket certainly is not quite so straight forward. But I think the OP you are responding to has something right when they describe it challenging to escape the easy/addictive and replace it with the difficult/beneficial.
If you only characterized exercise as "practicing picking up a heavy weight and putting it over there. Why do you need to do this? etc." then certainly the benefits can seem ridiculous.
That there is no direct practical need to learn Spanish, doesn't mean learning to speak it doesn't garner ancillary benefits.
My point was that people often seem to romanticise fairly arbitrary personal development goals as being a lofty intent, but when push comes to shove you'll find them in front of the TV or playing a game. What does that say about our internal reward system and the value of forcing yourself to do something that you tell yourself you'll enjoy over something you genuinely enjoy? The idea that entertainment is a "lower pursuit" and learning arbitrary skills is a "higher pursuit" smacks of social construction.