It's amazing how often "Hey, thanks for reaching out, I'm interested. Can you tell me more about the role?" results in the conversation ending right away. Probably over 50% recruiters that contact me do not reply back after that very polite and neutral response.
Many who do keep the conversation going have not read my profile or resume carefully, so I'll give them a summary of the types of work I'm actually interested in, which is never what they contact me for, and politely decline to move forward with the (usually way too junior) role they are looking to fill. That will almost always end the engagement.
Sure, it's a lot of noise, but filtering is very cheap: the time it takes to reply back. My actual success rate with recruiters probably pretty average. Of the eight or so jobs I've had in my ~20 year career, about three were obtained through recruiters, two times through in-house staff, once through an external recruiter.