There's a flaw in the setup. A toolkit will _never_ stop being useful
until/unless that particular _user_ stops finding uses for it. In fact,
the usefulness of a given tool is all in the eye of the user.
Are you saying that e.g. NetLogo, AgentSheets, and Swarm all have the same uses, if only the user finds them?
.... a person picking a
tool kit has to sit down and examine her own requirements .... She then
has to be skeptical and critical of the answers to those questions ...
Assuming that the new user knows what he requires the tool to do (I did, and it sounds like the cat modeller does too), the question is still which toolkits fulfill those requirements. You suggest asking the developers of each tool, one by one, but these are not easy questions to ask, because you're coming with specific requirements. You can describe your model to the person you ask, but whatever detail you give, they are going to give the same answer (they're own favourite, or "sure" if it's a yes/no question). In my own search, I eventually did ask the right questions, but not all of them, and my choice was not the best because of this. Specifically, I could not confirm that other toolkits had the capabilities I needed, even though they would have been better for my purposes. What I think will especially help the new user is something to read to allow him to judge the suitabillity of a toolkit himself.
And before investing in learning it! Is everyone to learn the use of every toolkit, and the programming languages they're based on? This will forbid its use to many people who see value in simulation, but happen not to be programmers. (Don't get me wrong - learning to program was my best move in 10 years).
Now if every new, non-programmer user will begin with analogous questions, I suspect that somewhere they will have been brought together. The question is where...