Doesn't hurt to call back recruiters if you're interested

Maintaining a good relationship with recruiters will pay off sooner or later. You'll never know when u'll need them.

Learn more about the job opportunities, get a sense of the job market, and tell them honestly your situation (e.g. stuck in GC application and can't change employer for a while). You can ask them to check back in half a year or so if you're really interested.

If you're happy with your current job anyway, you don't have to waste your time calling them back.