Do human accomplishments have long-term meaning?

It really depends what you mean by "long-term" and what you mean by "meaning". If "meaning" is understood as "having consequences", the consequences of some accomplishments have been significant for centuries, and occasionally for millennia. Roman engineers perfected the making of concrete two thousand years ago, and it remains a profoundly significant technology. If "meaning" is taken more as a spiritual term, this may not be a particularly "meaningful" accomplishment, as compared, say, to the widespread suppression of blood sports in the last 100 years.

But the whole of human history is just a drop in the bucket when compared to the life of the earth, or even more so, of the universe. If "long-term" is to be viewed on a cosmic scale, human accomplishments, even those with the most significant consequences and highest moral value, are a chirp in a vast ocean of time.