I'm not convinced Wikipedia is somehow profoundly not an encylopedia. Part of the reason your post doesn't convince me is because you criticize Wikipedia for not being "on par with the Brittanica" without specifying what you think exactly that par is, or what exactly you think "the concept of an encyclopedia is". It's difficult to have a conversation about these things without understanding what you view those things to be.
I know that I don't get the same freedoms with Brittanica I get with Wikipedia: I'm not allowed to distribute verbatim or edited copies of Brittanica entries. These freedoms translate into practical outcomes for most people, most notably the main means of keeping Wikipedia viable and an (apparently) mainstream source of information. By contrast, if someone wants to build on what they view as Brittanica's articles they have to negotiate with Brittanica to do that (and I've never seen anyone do this) but I know of projects that build on Wikipedia. Many articles I find interesting and worth listing in an encyclopedia are simply missing from Brittanica but are present in Wikipedia, such as why Brittanica thinks "GNU/Linux" and "Linux" are the same (which is both inaccurate and unfair) while maintaining that the former is an operating system and the latter a kernel (which is accurate and fair).
I have no changelog for Brittanica, so I have nothing to point to there that compares with what I can get in Wikipedia's changelog. TFA implicitly shows the value of changelogs for identifying how long edits have remained and who edited what when.
As for editing by non-experts: I don't know who edits Brittanica's many editions (including the paper editions) nor do I know what their qualifications are. I find this to be roughly equivalent to Wikipedia because I don't know who edits Wikipedia either, nor do I know their qualifications.
I remember some years ago reading an article by a Brittanica affiliate who essentially proposed to weigh Brittanica and Wikipedia on an evaluation of one obscure point he knew something about. Not only is that bad surveying, but it invites critique that can be used against Brittanica just as easily. I recall being struck by how behind the times Brittanica was the last time I saw it, particularly on the free software movement, a topic I know something about. I found the lack of coverage in Brittanica telling. Where Brittanica had something to say on the matter, I found Brittanica made the usual errors and confusions people make when they've only been exposed to "open source" (such as attributing what Richard Stallman's actions with "open source" despite historical contradiction and Stallman's own words and deeds); open source movement's philosophy, practical outcomes, or history isn't the same as free software and it's a shame history and contemporary evidence weighs so lightly for Brittanica.