Horrible editor -- and why contributing has declined
I ran into it not long ago when I went to correct a broken link in an article. I couldn't figure out how to use it and this is the kind of thing I do for a living. It really is the worst WYSIWYG editor I've ever encountered. Knowing they dropped a bundle into making it is...very discouraging.
The reason Wikipedia is having a "long-term decline in active editors" is due to the fact that there are *far* more people out there policing others' work than there are people being productive. It's a lot easier to shred what others do and consider yourself an important contributor than it is to put time into doing things which others will tear apart. I'm not talking about unsupported or poor quality content or images which stretch the limits of "fair use" (or vandalized content). "Uncontributing" can be stunningly egregious: an example, taking someone else's image, cropping it, deleting the original and uploading the "new" image as their own. I'm not even starting in on what happens if you don't agree with what's been done.
It takes very little time to challenge what others have done and fast track the content out of existence; it's onerous and extremely time consuming trying to prevent contested material from being eliminated (and forget attempting to correct a situation like the highjacked image scenario described earlier).
I was very excited about Wikipedia initially and invested a lot of time in contributing in positive ways. Now at most I'll correct poor English, remove broken links or clean up poorly formatted details (references, etc.). It just got too exhausting doing more, and when it's clear the people spending the most time are doing so by wiping out others' work, honestly, it's pointless.