The Heavenly Dao is unfair. People are born unequal.
Some are born with a Heavenly Spirit Root, and their path to the Golden Core is smooth and unobstructed. Others are born with mortal bodies, doomed to spend their lives struggling to make ends meet and laboring over trivial matters...
And then there are people like me. Though I have a spirit root and a chance at immortality, my cultivation advances slowly and every step is difficult.
Those with poor spirit root aptitudes must "comprehend the Dao" to break through a realm. Fail to comprehend it, and you'll be stuck at the bottleneck. No matter how hard you try, it'll be useless.
The demonic path doesn't care about that!
As long as you can break through, any means will do.
The Heavenly Dao is unfair, so don't blame the people for turning demonic.
The demonic path is still a path, and demonic cultivators are still cultivators!