I drafted a very unguided response to this on the chat, so here's a more constructed version of what I spoke of there.
I don't believe anyone, not even those of us who oppose game recs and the like, are intending to be elitist, and I certainly hope the site doesn't appear or aspire to be such. Nor do I think that our motive is to be exclusionary. But it is very difficult to be able to support building repositories in the very same system that we're storing our standard Q&A.
In terms of keeping the site healthy, I think we will find it difficult to continue support for repositories in any way that will allow it to both function within the site's mechanics and remain truly useful to the people who actually will come to us for repositories.
There is such thing as expert knowledge in building repositories. But what many people don't grasp is that the experience and skills for maintaining good repositories is much, much different than the experience and skills used for the rest of the Q&A on this site. And even now with all of the support that lists do get, I'm not seeing a whole lot of the actual experience necessary for maintaining expert repositories. This is where the statements of "game recommendations don't require expert knowledge" come from. Any community with sufficient breadth (which we notedly have) will be able to compile a list of games with a certain quality or feature by virtue of how many experiences are available to draw from. But to be a real expert repository, it would require high levels of research and maintenance.
An expert is someone who can provide a solution to a question, but this isn't necessarily based on quantitative experience and skill. For a traditional question, an expert has two approaches available. They either know the answer already and can post it when they see the question. Or, this expert is a great researcher, so they use resource management and contacts to obtain high quality information. These are the experts who will see a question without an answer, and decide that they can go out and figure the answer. Or, when it comes to gameplay, they might fire up the game and try repeatedly to see if they can find the proper solution. Some people walk both paths, experience and research. But what is important is that they are driven to provide solutions, and they get rewarded for it.
In terms of handling repositories, our experts of the first class are rather partial at the job, while we don't seem to have a strong drive towards the second level of expertise. We actively discourage individual users from providing more than one option to the asker by enforcing a "one game per answer". For rating purposes, this makes sense, but in terms of building a repository it is very poor. Some people will actually post multiple answers, but otherwise it appears that the general course of action is to post your favorite game that qualifies, and leave it to everyone else to fill in any you didn't list. And while I obviously have no evidence in either direction, I don't think our approaches to repositories really encourage experts to go out of their way to find qualifying games/mods that they don't immediately know. We're not Consumer Reports, after all. So our repositories are going to be generally low quality and based only on acquired experience of the total community.
I'll take my closing note to address your middle question. "What types of questions attract/repel 'experts'". I'll tell you what will repel these experts: the fact that there's little for them to gain here. Because everyone is infatuated with using votes to represent popularity of a suggestion instead of quality, Community Wiki is being taxed to allow these while preventing impure reputation gain. This means that not only do the experts get no feasible rewards for their contributions, but their association with their contributions is much less. As has been stated, part of Community Wiki's purpose is to detach the importance of linking the provided information from the user(s) who provided it. So despite what are probably a wealth of talent and knowledge in their field, these experts will never make a recognized names for themselves nor climb the reputation ladder without drawing from the other class of expertise that we address in this site.