A good example of the difficulties is outlined in today's featured article on the Island Fox. The bit on the main page includes the sentence "Its small size is a result of [[island dwarfing]], a kind of [[allopatric speciation]]". Come again! To find out what that means you have to wade through the technical article [[island dwarfing]] and [[allopatric speciation]] - and to begin to understand the latter, you also have to try to understand [[speciation]]. I think it means - "It is small because it is on a small island", but why not just say that?
It *does* say that. Anyone can understand that this is what "island dwarfing" means. And it says some more too, this phenomenon has to do with something called "allopatric speciation". If you're not in the know about that you can read the relevant article, helpfully linked to. If you're not interested in knowing you skip the link and move on. And it's not unreasonable to use the word "speciation" in an article about a species. You wouldn't explain what a "diesel motor" is in an article about a particular type of truck.
I'm sure there are pages where Wikipedia is unnecessarily written in an inaccessible and technical style but I don't think this is a very good example.
The risk in always trying to simplify down to the level of an absolute beginner in the relevant field (zoology in this case) is that the article can get cluttered or information lost.
Of course this is a matter of good taste and balance and reasonable people can disagree.
Regards, Haukur