Think about what makes travel challenging in real life
First there is planning:
Where will the party go?
How will they get there?
Where will they stop along the way?
Which routes and territories are safe?
Which areas or towns should be avoided?
Then there is provisioning:
What supplies does the party need?
What tools or other items will they need?
Throw the party against large numbers of low-level NPCs or area-appropriate animals.
If they're traveling through the wilderness, it'd be plausible for them to encounter an ambush by bandits, demihuman tribes, or military forces that might take an issue with their presence, resulting in combat. Similarly, when you're in the wilderness, it shouldn't be a ...