Quote interpretation? why stupid last forever?

Question

Youth ages, immaturity is outgrown, ignorance can be educated, drunkenness sobered, but stupid lasts forever. Aristophanes

Answer 1

Unlike ignorance which can be educated, stupidity, unfortunately, is cyclical foolisheness.

An ignorant person might not know any better, but will take the opportunity to learn and develop him/herself.

A stupid person, however, will take the same opportunity and proudly defecate on it. Even if he or she praises a good thing, a wise thing, a good opportunity, their willful pride and DELIBERATE refusal to discipline themselves to appreciate and embrace the better qualities of life gives them more satisfaction than a moment of sincere forward change.

And sadly that's why stupid is forever-- it never chooses to change.

Answer 2

All of the things that are listed before "stupid" are things that can be changed in a positive way, or, can be "fixed".

Youth ages

immaturity is outgrown

ignorance can be educated

drunkenness sobered

Have you ever heard the saying "You can't fix stupid"?  (Ron White)

One definition of "stupid" is "foolish".  Another is:  "Tending to make poor decisions or careless mistakes."

The author is saying that "stupid" can NOT be fixed, and, therefore, lasts forever.