Quest to level is a design anti-pattern that forces player to take quests to level.
Its both detrimental to quest quality and leveling.
1.Quests become simplified exp/loot gathering operations.

2.Quests are further reduced in scope/lore significance and used as excuse to move player around content(aka railroading).

3.Leveling becomes task-oriented routine, forcing player to perform a fixed role regardless of choice(not taking quests is usually detrimental to leveling speed).

1. using non-exponential experience system e.g.
2. removing significant quest rewards and relegating quests to pure-storyline/pure-lore achievements.
3. not creating quests without significant background material that justify their existence in the first place. Rich, complex quests instead of tasks.