But it's not very helpful in understanding the nature of ourselves, which is where science remains a weak tool.

It's a mistake to conclude science is a weak tool just because it produces less certain results in the social sciences. "Weak" is a relative measure, so science is only a weak tool if you can actually demonstrate the existence of a much better tool.

It may be a weak tool, but it's the only tool that we know actually works.

Also, as science helps us advance technology it becomes a continuously stronger tool.