("always verify your references").
The trick, of course, is knowing where to look.
I am a bit of a bug on British royal genealogy, so I have a couple of websites on tap. I'm pretty solid on the British royals without having to check, but when I get off into collaterals like the Oldenburgs, I have to go look.
And once you get into Queen Victoria's era, they are so intermarried that the Guelphs and the Oldenburgs and their various collaterals keep crossing generational paths.
OK, I’m still impressed! :^)
As you say, a lot of “knowledge” is knowing where & how to find the relevant info, quickly when necessary. The Internet has made a lot of that easier, but there are mountains of irrelevant stuff too, so it takes a practiced mind and touch to burrow though it efficiently.