I think that's right, but in another way Wikipedia does keep the plebes out:
When you defend a reverted change on the talk page all too often you get something along the lines "I don't care about this discussion, it was an IP anyway. Stay away!".
Wikipedians often see "IPs" as vandals and don't even pretend to judge on the merits.
Together with some "ownership" feeling that many Wikipedia users have regarding "their" pages, it makes for a very unproductive and frustrating experience for a casual would-be supporter.
Unless you're willing to really commit to Wikipedia, learn all the jargon and be a part of the power games, Wikipedia is effectively read-only.
As an "IP" you're mostly restricted to fixing typos.
That's perfectly fine, but a stark contrast to how the project is painting itself.