Earth has an incredibly diverse biosphere—jungle, temperate forests, vast oceans, mountains, deserts, prairie, etc. And because of the tilt of the axis and its rotation around the Sun, it has the four seasons. How common is this kind of single planet diversity in the Milky Way Galaxy? Is it more common, or less common throughout the rest of the universe?

The diversity is less common throughout the universe compared to the Earth for the reasons we have stated. The geographic circumstances with the rotation and the polar axis, such that there are wide variations in temperature across seasons, does create special demands on the life forms present for them to survive. This is, in many ways, a benefit to the development of the divine human species as it represents a natural challenge for them to deal with and this learning curve has served you quite nicely to literally weather the storms and devise ways to cope with adversity, which is a character-building exercise that will serve you greatly in all that comes in your future, so nothing is wasted in terms of what humans experience.