It's not a myth (I wrote ATS systems, and you usually just pay some third party to do the core parsing job as a library or a service and take your failures on the nose) but at the same time most recruiters are NOT going into past resumes and filtering through them, and most of the wide shot resume hits you get on linkedin are for the lowest tier of jobs.

Almost all recruiters are "most recent resume in" type of folks or "curated long term list" type of folks - they'll either circle you for years trying to get you hired for something or they'll forget your name in 25 minutes.