Just use JSR[0] and only deal with npm when a project forces you to do things backwards. Since JSR packages are available on npm, there's nothing lost.
JSR says "here's a way to leave the original ecosystem alone, but have a better-fitting ecosystem that does the things you want". (not sure about the 'jsr doesn't change' bit? It literally requires ES modules, in lieu of common js modules).
Seems pretty relevant, to me, but YMMV. I understand it's not a direct answer, but it seems as relevant as "here's typescript" to someone saying "we should add types to javascript".