Thing-hood in Buddhism and meaningfulness I often struggle with feelings of despair about not so much that I will die but my mortality, my insignificance in a time as time never ends.

But it also occurred to me that actually everyone is in the same boat (so to speak) and so as long as we don't let things define our value, then maybe life has meaning and value.

Is that anything to do with emptiness, or is emptiness more an ontological doctrine than anything about value and meaningfulness ?
I think you should contemplate thus:


  There were many Buddha's before your current Buddha but their significance and influence has come to an end. My influence on earth is comparatively more insignificant. Any influence or value you bring on the earth has a finite time span. No one is indispensable in the long run. In the grand scheme of things you cannot attach a meaning off significance to your existance, life and influence.


But only until your polarity in looking for significance of existance is subdued. For a lasting solution you have to do Vipassana.



Looking for meaning or lasting influence you are trying to exert some control to you environment which you cannot and lead to misery as if it does not materialise you might think of yourself as a failure. You can try without being too attached to result of your influence.

Trying to give meaning to any thing, you are dealing with concepts and perception. Reality will always be different, hence disappointment. So trying to give meaning to anything will not be entirely satisfactory.