Frozen has a story. A simple one, but it does have one. after the events of the film, Arendale decides to throw an annual Summer Snowday Celebration. As part of the festivities, you get to go on a tour of Elsa's I've Castle. So you start in the forest with Olaf and the Trolls setting the scene and the plot, you go up the lift hill to the palace, and see Elsa. Then you leave and see "fire works" above the regular castle. It's simple, but it works. They do just kinda use that plot as an excuse to string together reprises of all their songs.
The only real problems with Frozen are very simple, unexciting environments (the ice palace itself is particularly underwhelming). That makes it feel way more empty than it is and, I believe, where most of the complaints about it being short come from. It's not really short, there's just a lot of empty or underutilized space. The other big problem is its location, but that's been discussed to death.