A telephoto lens does more than make distant things look closer.
It changes how you see.
Compression Changes the Scene
Long focal lengths can make distant elements appear visually closer together.
Mountains, trees, buildings and subjects can stack into a much tighter composition.
This can simplify a scene dramatically.
Backgrounds Become Easier to Control
With a long lens, a small change in position can make a distracting background disappear behind the subject.
That is especially useful in wildlife photography.
You are not only choosing the subject.
You are choosing what exists behind it.
Reach Has a Cost
Long lenses are heavier, less forgiving of camera movement and often more demanding in poor light.
At 600mm, tiny movements are no longer tiny.
That means shutter speed, stabilization, technique and support all become more important.
What Actually Matters
Do not buy a telephoto lens just because more millimeters sounds better.
Longer reach changes the visual language of the photograph.
It gives you isolation, compression and access to subjects you simply cannot photograph with a standard lens.
But you still have to make the photograph.