In my opinion Wikipedia is not a reliable source. If I am not allowed to use it in my essays for college (and was not even allowed to use it in middle school), it has no business being used on Wikitree. Just like here on Wikitree, anyone can edit a profile on Wikipedia. However, Wikipedia allows LITERALLY anyone to edit, even if they don't have an account. I personally have spread untrue things on Wikipedia (I was in high school and it was something dumb all my friends had been doing at the time, please don't judge me), and you see different things like that all the time. It's just not reliable at all.
However, Wikipedia does cite all of their sources (similarly to Wikitree) at the bottom of profiles. If you open up those specific sources and find the info you're looking for, you can more than likely cite them.
But please don't cite Wikipedia.