Priorities do change along with environments to some extent. In very cold situations, shelter is the top priority. You can go a bit longer in the desert or on a tropical island without shelter. It will become important, just not in the first 3 hours. What you use for shelter will also change along with the environments.

Water is always a very high priority, but where you find water, and what you take to collect, purify and store the water may change.

Instead of a fixed list of essentials, it is better to address it by priorities, which do change a bit. A good understanding of the environment you are going to be in is always essential, maybe the number one essential.