The essence of Frankenstein was about human nature. Specifically that we hate ugly things and love beautiful things even when the beautiful are evil and the ugly kind [1]. The only reason the creation wanted to destroy the creator was that the creation had no place in this world and was denied even a small amount of peace by the creator that condemned it to existence.

[1] When the beautiful doctor started working with dead bodies and so on, it was a "phase" he was going through. Not a bad person at all. When the monster saved a man's daughter from drowning he was shot for his trouble because something so ugly could only be evil.