What are some reasons that T. S. Eliot's "The Waste Land" is considered a critically valuable poem?

T. S. Eliot’s “The Waste Land” is valued as a poem by many
readers for the following reasons (to mention just a
few):

• Its skillful use of allusions (implied or
  explicit references) to other texts


• The ways in which it
  incorporates such numerous allusions into its own peculiar
  unity


• The ways in which whatever unity it possesses is
  subtle and suggestive rather than overt and rigid


• The
  ways in which its fragmented form and imagery are appropriate to its larger theme of
  social and cultural fragmentation


• The ways in which it
  suggests a journey into the underworld without making that theme simplistically
  obvious


• Its literary sophistication and daring
  experimentalism


• Its break from traditional literary
  conventions that had come to seem, to many, stale and
  predictable


• The ways it challenges readers to think
  rather than making them mere passive recipients of prepackaged thoughts and
  emotions


• The fluidity of its
  structure(s)


• Its use of recurrent images, such as water,
  to achieve a subtle unity


• The ways it skillfully uses
  juxtaposition (abrupt contrasts) to imply its points rather than openly stating
  them


• The ways it tries to make the past seem relevant to
  the present


• The ways it alludes to a whole range of
  earlier cultures, not just (predictably) to classical Greece and
  Rome


• Its focus on such undeniably important themes as
  life, death, and the possibility of at least some kind of symbolic
  resurrection


• Its social
  relevance


• Its skillful use of ambiguity, irony, and
  subtle suggestiveness


• Its almost encyclopedic or epic
  ambitiousness, despite its relatively brief
  length

Yet there is also much to be said for
the poem simply in terms of its sound effects. Consider, for instance, the opening four
lines:

April
is the cruelest month, breeding

Lilacs
out of the dead land, mixing

Memory
and desire, stirring

Dull roots with
spring rain. (Italics and boldfacing
added)

Note the way the
italicized verbs are given maximum emphasis by coming at the ends of their respective
lines. Active verbs (suggesting life and vitality) are juxtaposed with the dead
landscape. Note how the repetition of such verbs in those places contribute to the
rhythm and music of the poem. Notice the skillful use of the bold-faced alliteration,
and notice, too, the balance of “Memory” and “desire” (one focused on the past, the
other focused on the future) and of “Dull roots” (adjective/noun) with “spring rain”
(adjective noun).  Whatever “The Waste Land” may or may not mean,
it is often a powerfully well-written work, vivid in its imagery and striking in its
sound effects.