Ignore the advice of father is in the post-1970 Little Mermaid
Considering King Triton’s “advice” amounted to “no surfacing even when there is no humans in proximity” (you know that merpeople are more likely to see us coming before we see them coming, right?), and, I should add, he implied he wanted to commit genocide against humans (the whole “One less human to worry about” thing), I’m pretty sure that is “advice” I wouldn’t even obey if my own parents gave, heck, my own parents or even grandparents would not obey regarding THEIR parents, and I share my parents politics in that I’m conservative. Heck, there are a few people who actually went against their parents in Nazi Germany by fighting AGAINST the Nazis, and NOT for the Communists either.
Besides, at least Ariel actually worked hard to save her dad and avenge him and tried to fix her mistake, which is against what post-1970 would advocate (if anything, post-1970 would advocate having kids act like, say, Francis from Malcolm in the Middle).