WikiTree is a repository, not a source. The goal is to create one world-wide, documented, family tree, collecting and recording information from many sources. People contribute and collaborate, building on what others have added. People join and generally add their immediate family, then go back a few generations. Many folks don’t have go go back too far to find a connection to a profile that’s already here, and Voila! You are part of the big tree. For others it’s harder to connect, but you have the benefit of a huge community of serious genealogists here to help you.
Getting started can take some effort, and some folks are put off by the requirement to document your ancestors with reliable sources, but once you get going it’s great!