Quite the opposite, actually. Can you imagine the uproar if anybody found out that United didn't make every effort to operate the flight? The second-guessers already come out of the woodwork any time there's a timeout, suggesting that UA pilots don't really want to fly and would prefer to cancel just to enjoy screwing over the customers. Now you want them to actually do that?

OP: The reason that the crew timed out five minutes after leaving the gate might have been incompetence, but it seems much more likely that five minutes after leaving the gate is when they got the final word on their wheels-up time, and that wheels-up time was too late for them to operate the flight legally.