A quick Google search for the definition of teleology brings up two possible uses for the term. The first is philosophical and the second theological.
Philosophically speaking, teleology is “the explanation of phenomena in terms of the purpose they serve rather than of the cause by which they arise.” Theologically speaking, it is “the doctrine of design and purpose in the material world.” While these two definitions are related, teleology grounded in theology represents an extreme application of the concept, especially as far as it emphasizes design.
Sadly, theological teleology’s insistence upon hogging the cosmic stage by promoting capital ‘T’ Truth has given purpose a bad name. Worse, it has only encouraged our contemporary tendency to favor either/or thinking at the expense of nuance and context. Whether we should emphasize cause and effect or purpose will always depend upon the context, and in any case neither way of seeing the problem should ever be entirely excluded.
When cornered and forced to choose between fundamentalism and its associated insistence upon ideas like creationism (a.k.a. intelligent design) and materialism’s more “evidence-based” approach, materialism won over all the minds that really mattered even if many hearts were still left unmoved.
The long and the short of it is that teleology (i.e. purpose) has suffered considerably over the past three centuries or so, particularly in the West. While it will always prove impossible to drive purpose entirely from lived human experience, it has proven possible to drive it underground and erode a shared sense of purpose in favor of highly individualized identities.
But as is so often the case when one paradigm seems to have triumphed decisively over its predecessor, materialism’s advocates were not satisfied with demolishing ideas of a literal personal god capable of designing the universe in advance and building it from scratch. The idea of purpose itself needed to go, along with all associated supporting philosophical arguments. In other words, from the tiniest particle to the cosmos itself everything needed to operate deterministically.