[pluma]

Sure, but my current ecosystem is npm. For browser-specific substitutes to node-specific code I simply use browserify. If I decide React is boring, I can switch to an entirely different front-end without changing anything else. For stuff that isn't on npm I have to work with bower or something else, but that (i.e. ecosystem-external dependencies) is a problem in any application, not specific to npm.

With Meteor, you're developing Meteor apps. Sure, you can put a different front-end in it or replace its server-side with an API compatible equivalent, but that's like saying you can use Django without its template system or ORM (if you don't know anything about Django: you can, but Django's built-ins provide a lot of synergy that you can only get from tight coupling).