In those cases, perhaps the playwright ought re-cast the action. Now there s forward motion. Now the character isn t whimpering but instead of trying to make a solution. Now the character can exhibit brains and guts trying to solve a huge problem. That s going to be more interesting and has a much better chance of being stageworthy.
Critics voice that complaint about some plays.
The question means there s a fatal problem. We can find the answer by looking at relatives of the solo play the soliloquy, as in Shakespeare, or the solo number in a modern musical. I think it helps the playwright to give the character in a solo play that same driving compulsion. The solo play is complete in itself, crafted with a beginning, middle, and end, but a monologue is an extract from a longer work. The solo play is much longer than the audition piece, which typically must be limited to perhaps two minutes.