I've heard the same advice just as many times. I have been forced to conclude that the people who are giving this advice either don't know what they're talking about, or they're thinking of a very specific connection they have with someone that is impossible to replicate on command.
I'm a mid-career dev with about a decade and a half of experience, and I have failed at mentorship from both directions.
I have failed at being an effective mentor. I have reached out multiple times to less experienced people who say they're looking for a mentor on various forums. What I offer: my first-hand experience working in Silicon Valley; realities of the industry; tech stacks that are actually in use at various companies; interview prep or advice for self-study; interviewing experiences I've had and what I've found to work, as interviewer and interviewee.
After a couple rounds of email or video calls, the prospective mentee loses interest and we let the conversation die. I get a gnawing feeling that they were looking for a job hookup. Maybe I just suck as a source of value?
I have also failed at finding an effective mentor. I could really use someone who is on a path similar to mine, but 5-10 years ahead. I'd love to get some relatable, trustworthy advice about career trajectory, picking the right company to work for, how to know when a team or project is right for you, and what to do about it, what to specialize in and how, what to do about continuing education, etc.
What I usually find instead is aggrieved people who just want someone to listen to their tale of woe, or (slightly better, but still not good enough) people who are further in their careers, but a bad personality match. For example, they might offer advice about how to find jobs where you do as little work as possible while your boss ignores you, or people who want to get out of tech and flip houses or something.