Formally and explicitly stated the argument from design is written such as:
"The origin of complexity* [see below for definition] from non-complexity is best explained as the result of an intelligent designer, rather than as the result non-intelligently guided natural processes".
*complexity defined for example as complex systems composed of multiple componet parts or complexity defined as organized specified complexity.
Note that the above argument is dealing with 1.) complexity defined specifically and 2.) with complexity that has an origin from non-complexity. To use an analogy the origin of the multiple componet complexity of a sophisticated "watch like device" if found on Mars would be taken as strong evidence of being the result of an intelligent designer, rather than as the result of natural processes. (In this case no one-not even anti-creationists would object to complexity as evidence for design).
However, when it comes to complex biological systems anti-creationists protest and claim that the argument from design is somehow illogical, requiring an infinite regression of designers, or other logical fallacies. Their argument for example is that: "If complexity requires and intelligent designer then the intelligent designer must himself have required a designer, and his intelligent designer a designer, etc, etc, !!"
In order to do this though they do they omit the fact that the design argument is explicitly or implicitly dealing with 1.) complexity defined specifically and 2.) with complexity that has an origin. Their method is to automatically define all types of intelligent designers as "complexity"; and then to also ignore the fact that the design argument is dealing specifically with complexity that has an origin, and not any other.
By doing these things they twist a logically valid argument from design into a strawman requiring an illogical conclusion.