Tell that to people who are successfully using the theory to solve real problems in various fields of biology:
Such as conservation of endangered species:
http://evolution.berkeley.edu/evolibrary/search/topics.php?topic_id=27
Agriculture (beyond mere artificial selection breeding):
http://evolution.berkeley.edu/evolibrary/search/topics.php?topic_id=26
Medicine:
http://evolution.berkeley.edu/evolibrary/search/topics.php?topic_id=25
Etc.
The ones for species conservation are particularly important, because they emphasize the value of "macro"-evolution: How species are related to each other, not merely how one species changes in small ways over time. It is often the case that we have to infer information about a rare species from other life forms related to it by various degrees.
Many of those agriculture articles talk about the hidden natural effects that emerge from our attempts at artificial selection. Artificial selection is
not entirely artificial: Nature ends up controlling important areas of the effort, as well, in ways best understood in terms of evolutionary theory.
The medical examples might be dismissed as largely "micro-evolution". But, you don't see Intelligent Design being applied to any medical research, in any realistic, practical manner. So, people are going to work with what they
can work with...
...And The Theory of Evolution WORKS in all of those cases!