Like any online tree, the information on WikiTree is only as good as the sources. Unlike most sites, WikiTree has a concerted effort to source and prove every connection. Still many connections were created by unsourced and flawed gedcoms, so you still need to be cautious. If you add data from WikiTree to your own personal tree, you should evaluate the sources used and decide for yourself the confidence of the information.
If you find any errors, please fix them and add your sources. That is what WikiTree is all about.