What are the crises and complexities regarding the characters in Waiting for Godot (and how are they involved in their progress)?
This is an excellent question.
As the work is an absurdist tragicomedy, the answer to this question is a broad and equally complex one. While the text indicates that the protagonists spend every day in a similar fashion, many readers suggest that the crisis that Didi and Gogo face are in their complete inability to act and force any semblance of real, demonstrable change in their otherwise meaningless existence.
The complexity of the play may, in fact, lie in its sheer -- and at times, mind-numbing -- simplicity. The play is a tautology; all of the play's action is summed up in it's title. Vladimir and Estragon are "Waiting for Godot." They can't move. They can't leave. And they can't change their lot in life. Why? Because (as becomes a repeated joke throughout) they're waiting for Godot. They are so paralyzed by their obligation to wait for an unknown traveler that they spend every day of their lives doing nothing of substance.
Ultimately, your question about the progress of these characters is fundamentally tied to the reasons outlines above. They can't move, but they want nothing more than to make meaning of an otherwise meaningless existence. Until Godot arrives, however, they can and will never make any real progress -- thus the author could well, in fact, be suggesting that the lives of these two men is ultimately meaningless.