Sometimes there are good and important tasks whose importance is clearly communicated, but which go undone. But, in my experience, the majority of tasks like this might need to be either (1) better specified so that they can actually be understood and completed or (2) communicate better what the importance of the task is with an honest evaluation by both people and comparing to the value of other workload priorities at present.
We have a tendency to believe that our task is the most important one right now, and that our ideas are the best ideas, without understanding what someone else is really doing and without taking an objective look at why something else could be more valuable.
We can use that ourselves when we try to assign tasks to others. Are we being fair to them, their priorities, and their workload? Maybe our task isn't all that important? Maybe we can communicate better with them to understand the totality of what they value, or maybe what they think a better alternative to our task would be. After all, Alexander the Great asked his troops if they had any ideas for strategies... and he won a lot.