Those most likely operating out of the same boiler rooms as tech support scammers who have pitch terrible roles and employ a spray & pray approach where it's just a spam campaign with very little effort on their side. Those are a waste of time, the roles are terrible and are pretty much never matched to your profile, and when you go through anyway the recruiter will not provide any value (I had one insist on me writing a short resume of my profile... I mean you have my resume in front of you, why don't you do it?).
The rest which are typically alright. Again, quality varies, but I haven't had any outright "bad" experiences with any of this category. On the top-end of this category are those that understand the industry very well and what you're looking for and will only pitch you the right roles at the right time. The right recruiters can essentially be your sales team and are absolutely worth having on your side.
I suspect most people's interactions here would be exclusively those from the first category as they're the ones that typically send unsolicited spam. The second category will typically show much more restraint in reaching out out of the blue, so unless you explicitly seek them out you may not even be aware they exist.
