Leveling during Vanilla took was long and tedious.
- Quests only gave a very small amount of exp
- There weren't enough quests in zone A to level you up until you could start Zone B. You either had to keep switching between them zones, or spend long hours farming mobs.
- No mounts until lvl 40 and the fact that they used to cost a lot of gold.
- Some classes (like priests) had a very hard time killing mobs. Drinking every other mob for 30 secs really slowed you down.
- You actually had to read, think and search when doing quests. There weren't any addons yet to help you
A lot of us, who leveled during early vanilla, still suffer from "levelingphobia".
When I started to level my main at MoP release, I actually had flashbacks, cold sweats and noticed myself shivering at multiple occasions.