Maybe SuperCollider Quarks Web Index and Add infos about each quark on website · Issue #117 · supercollider-quarks/quarks · GitHub helps?
As an occasional pd-lurker I found that the split from pd-vanilla and pd-extended to very unfavorable for the userbase of pd, see https://forum.pdpatchrepo.info/topic/12797/pd-vanilla-vs-pd-extended-why-such-a-mess - there should be a good reason to do such fork (b/c many will not follow if it breaks their code) and I fail to see a real justification for such a discontinuation - maybe so it is “nicer to maintain” - but at the same time is it? After 10+ years of software development I found monorepos the easiest to maintain - especially since sclang has no rock-solid dependency and test management system. In my experience the best way to manage a big code base is to have a really big test-suite, something where sclang could definitely improve.
Also - what would one consider core and what not? I found the programming languages with a big standard libraries (e.g. Python) to have a way more stable eco-system than something with essentially no standard library (e.g. JavaScript, the mess with jQuery, leftPad etc).
I also find Quarks quiet sophisticated, you need git installed and in my everyday “sc-teaching” I found that many people don’t have git installed and installing git, especially on Windows, is not a trivial procedure for users and many will not use any Quarks because of it.
I think it is important to keep in mind that many SC users do not have a focus on programming, so once you break their hard written code they may not follow a transition if they can’t see any gains in it. I would also not switch because there are many extensions I use which have not seen updates in 8+ years and I doubt they would be all compatible with such breaking changes.