This reminds me of a group of roommates I had in college. They played Super Smash Brothers: Melee for the Nintendo Game Cube perpetually. They played the same level--a flat level without platforms or items--over and over again for one reason--to get better. They had little interest in having fun and cared more about being the best.
One of our other roommates suggested that they play the game to have fun. They liked the suggestion and, as they began playing again, started to compete over who was having the most fun. My other roommate's comments had completely missed them.
Just sounds like your "other roommate"'s idea of what is fun was in different alignment from theirs. Rather than accept different tastes an attempt was made to coerce them (by use of negative language - "why not just play for fun") into playing for the same purpose he did. Unsurprisingly they found a way to have fun despite being forced into a new playing style.
The implicit assumption here is that the game is always more fun with items and platforms.
Personally, I find it more fun to try and become a better player. Learning new ways to glitch the system, how to counter different strategies. From a competitive view, the fun is reduced when things like the environment or randomly-placed items remove the "fairness" of the competition and favor one character over another.
My college roommates were obsessed with playing Final Destination in Smash without items and spamming cheap attacks to win. Guess that practice is more common than I thought.
It sounds like they were having lots of fun. When I was in college, we'd configure the random level selector to always select Final Destination, so that we didn't have to bother moving the pointer a few inches.
One of our other roommates suggested that they play the game to have fun. They liked the suggestion and, as they began playing again, started to compete over who was having the most fun. My other roommate's comments had completely missed them.