What are the didactic elements of the morality play Everyman?

Didactic means instructive, designed to teach or impart
information.  In ancient literature, this is very common, and is certainly appropriate
in some contexts.  The Bible, for instance, is heavily
didactic.

Today, however, when we say literature is
didactic that can be a negative, a pejorative.  A sermon should be didactic, a parable,
a fable.  But art, as we see it today, should not.  Using literature to teach or preach
reduces the art's value or quality today.

That wasn't
necessarily the case in the time Everyman was written, however. 
Plays were used for the purpose of promoting church doctrine.  That is what this play
does.

You can see this almost immediately in the play, in
the words of the Messenger:

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You think sin in the beginning full
sweet,

Which in the end causeth the soul to
weep,

When the body lieth in clay. 
(12-15)

 This is a play
designed to urge the audience to repent and not to sin.  In fact, now that I think about
it, we need not even read as far as these lines.  The words in italics preceding
the play state the didactic purpose of the play:

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Here beginneth a treatise how the High
Father of Heaven sendeth DEATH to summon every creature to come and give account of
their lives in this world, and is in manner of a moral
play.

The purpose
of the play is to promote morality.  That makes it
didactic.

Incidentally, and this refers to the quality of a
didactic work of art, Chaucer, too, writes in a way that, at least on the surface, is
similar to the way in which Everyman is written.  Yet, Chaucer is
considered to be one of the greatest writers ever to write in the English language. 
Why?  The difference is simple:  Chaucer uses irony.  Irony keeps Chaucer from seeming
to be didactic.  Everyman uses no irony:  it just directly presents
good and evil and tells you which one you better be if you want to avoid
damnation.