Morally speaking, the colonial leaders did have such a responsibility, at least from our modern perspective. Morally, there is no reason that these groups should not have been included among those who were "created equal."
Practically, though, they did not have any such responsibility. There was no way that people of that day and age were going to take seriously the idea that women and African Americans were equal to white men. If the leaders had included such language, it would simply have served to make the Declaration something of a laughingstock. It would have reduced people's respect for the document.
So, the leaders had a moral responsibility to be more inclusive, but practically speaking, it is probably better that they did not.
When the colonial leaders wrote the Declaration of Independence, they were explaining how the King of England was abusing the rights of the people. Since the colonial leaders were upset about the colonists not being treated fairly, it is very reasonable to argue that they had a responsibility to make it clear that the Declaration of Independence and its statement about equality included women, African-Americans, and other groups that were traditionally not being treated equally.
While it was common practice in those days for men to have more rights, privileges, and opportunities than these other groups, the colonial leaders had an opportunity to set a precedent by saying that treating people equally meant treating everybody equally. While the colonial leaders didn’t have an obligation to do this, they had an opportunity to really make our revolution a truly revolutionary event by taking this position.
If they really believed that we were fighting for freedom because we weren’t being treated fairly by the British, then it is fair to say that the colonial leaders did have a responsibility to make it clear that all people should be treated equally.