I think that jam games should be short experiences, because it is made in a small period of time, if a 1 week jam game has a large playtime there can be some reasons: the game require a large time to progress, like, large levels, hard puzzles, lots of text(this case is my game), not adding much new stuff during that time can make the player become bored quick, to have all that and still be a fun game that keeps players engaged you require lots of skill and experience.
There is too the case if the game is too easy, players get bored, if too hard, frustration. So much things to be aware when making a game, it all comes down to experience and knowing what to do.
People often have big game scopes for jams, i am trying to avoid that, creating a small experience that is more manageable for a jam short time, though i failed this time ,my game turned out as a visual novel, which are full of text and require large reading times, my friend did the writing and it is good, but doesn't know if it is enough to keep the player engaged until the end.
But yeah, some people won't like large playtime jam games because they want to review as many games as possible and so are expecting small experiences.