I wouldn’t fully agree. All parties being adults doesn’t inherently remove the advantage very large age and experience gaps can give to one party over the other, especially when one is barely adult. 18 or 21 is just an arbitrary number, and one doesn’t suddenly become smart about these things just because the law says they are now legally full citizens, responsible for their acts and for themselves.
But I also agree it doesn’t make age gaps between adults inherently negative. It’s just… complicated.