Chaosmancer
Legend
I really don't think associations in any of your example cases are nearly as strong as with rock gnomes, but yes, in general I would prefer a lesser number of conceptually broader yet thematically coherent races over the current situation of insane amount of stupidly narrowly flanderised races which still manage to thematically overlap with each other.
Really?
Wood elves are really only known for using bows and protecting the forest. That's it. That is their entire identity, how is that more than just "They are rangers"?
And Rock Gnomes have other things going for them as well. They are the more city and urban of the gnomes. They tend to be scholars, tutors and teachers of the urban areas. In other settings they are into the bureaucracy of empires. They also still do have a love of illusion and magic, even if they don't master it to the degree of all of them having the minor illusion cantrip.
Compare this to Mountain and Hill Dwarves. These are dwarves that live in mountains. These are dwarves that live in hills. Oh! And the Duergar, these are dwarves that are evil. Can't specify they live underground, because all dwarves do that.
The thing is, gnomes ARE thematically coherent. They can be conceptually broad if given the chance (notably, other than the Snirvfelbin which are the weakest thematically, there have been no new gnomes for a LONG time.) You just don't like them.