I think your own words on that game's comment section answers your question: ". . . the game is simply a platformer."
If it's "simply a platformer" then what's the appeal? The vast majority of people who come to Itch.io have played a platformer of some kind, so unless your game offers something special to that genre, there's not much incentive to try it out.
That being said, adding a gif of the gameplay would 1) make the game page more interesting and 2) show people what it looks like in action.