English Wikipedia has a "standard" for notability of people at [[wikipedia:Wikipedia:Notability (people)]]. Each language Wikipedia sets its own rules, so the standards that are linked to all the languages down the side of that page could well set different standards.
We can argue here whether that is still the appropriate standard for the Wikitree Notables project, but it what has been adopted for now.
If you find articles in Wikipedia that you don't think belong there because the subject does not meet Wikipedia's criteria for notability, it is possible to propose them for deletion, see [[wikipedia:Wikipedia:Guide to deletion]].
I agree with Dale that Wikitree and Wikipedia should not be used directly as sources for material in the other, but will add that it is quite possible that the articles, with quite different focus, could well rely on some of the same material, and certainly reading each other's articles could help us improve them both. A good article on either site should reference the sources that were used to write the article, so we can read the Wikipedia sources to help write Wikitree articles (and vice versa).
[confession - I have been a Wikipedia contributor for much longer than I have been a Wikitree contributor]