xmt

Some of them are definitely spammy. If they are vague about the job I pass or if they don't seem very knowledgeable and clearly haven't read my resume I pass.

Recruiters that specialize in your area are better. I've found linked-in recruiters to be better than job board recruiters. Just put some in demand skills on your profile and they will come to you.

I should also mention this probably works better if you already have a job and some experience and isn't so great if you are just starting or switching fields.

This. I've stopped applying to companies directly because it takes too much of my time and the response rate is too low. With a recruiter I'm pretty much guaranteed at least the first round of interviews with just a 15 minute phone call.

I imagine it's gotten to that point for a lot of job seekers.