I respectfully disagree that a 'directed' computer search of 500,000 names would take 'no time at all.'
You have to input names. You have to review the results. You have to check each set of results to see how it fits with other results that you have; it's like fitting together pieces of a jigsaw puzzle. The problem is that so many published genealogical records are garbage.
Getting into the DAR, SAR, DoC and other organizations was a source of pride or society in small towns and applications were often accepted based on one's family status and not the quality of research. Census records were taken once a decade. Wives who were married after one census year and died (childbirth, typhoid, smallpox) before the next never appear in a census - but the next wife appears to be the mother of the children in the census. Other genealogical records of the same family, based on a family Bible, will show an entirely different mother.
You can't reconcile those differences with a directed computer search and nobody, not even the LDS, knows which records are wrong or right for many families.
If 'directed computer searches' worked, then genealogy as a hobby wouldn't be so interesting . . . or so difficult.
The first problem is that in 1676 or thereabouts "they" held Bacon's Rebellion. As part of the compromise to bring an end to that situation, and to re-establish the legitimacy of Royal rule in Virginia, just about every male in the colony changed his surname. Some changed a lot; some changed a little; but Washington does not have any of those who did not change their surname in his lineage.
There's no simple way around this problem. The noble lineage of the Lee family has the same problem.