There are sooooo many details to be done.
First, they need all the permits, which don't fly in on a daily basis, then all the structures, wires, meshes, etc. need to be carefully set up, since they're recreating a natural mound and not a square house with a few details stuck on, that'll take some time. Then between pouring all the cement and molding the plaster, there's a long wait time for it all to dry considering they're in a subtropic climate. Add the details and animatronics inside the ride, a well as the ride structure itself, which has to be perfect in every bolt and detail, and you've got a highly complicated construction venture.
You really need to cut them some slack for doing their best to build this ride in the shortest amount of time possible, and since it's never been built before, there are a lot of "will it blend work" decisions to be made while building, and that can expand the construction time considerably.