What makes a problem skill is a combination of low exp, high focus, constant clicking and no real reward.
Agility is a mix of all of that.
Construction is good because it stands on its own with tons of rewards and its exp rates are insanely bloated while having a choice to take lower exp to save on cost
Slayer is good because there's tons of reward, variety and you get to make a ton of choices in how you handle it
Making a boring skill faster alleviates the burnout and fixes a few of the issues i outlined in the first sentence.
High clicking with more focus for higher exp is fine, higher clicking higher focus with low exp isn't.
Agility can't be afk'd so it'll stay higher focus regardless and most agility rewards aren't worth the squeeze, some shortcuts are great, but if you're leveling agility primarily for that, that's hardly a goal worth 250 hours of mind numbing.
For how much effort agility takes compared to most other ski...