People actively seeking a mentor are likely willing to consider the advice and tough criticism they get as points to self-reflect upon, because they want to improve. They want to become faster stronger developers. As common as that might sound I have found intentional yearning for self-improvement to be rare or severely misunderstood among junior developers in the corporate world. More common than self improvement is interest in specific technology stacks of the moment and persuit of near instant gratification.
EDIT
Actually, I can remember observing this behavior once as a junior developer. When I started learning JavaScript 12 years ago the real big deal then was Java. Compared to me at the time everybody seemed incredibly experienced and talented, but most of the developers were negligent to the point of horrid incompetence at the frontend skills even though this was a big brand web business and 90% of their efforts generated frontend code.
There were a few Java developers who did have a solid understanding of the frontend code, but they intentionally didn’t advertise this. I had to actively observe for it. After badgering some of these people it was clear they were willing to provide mentoring if I asked for it and worked my ass off to chase it.
What I learned the hard way is the people who made the best developers had a secondary skill they actively thought about more than their primary skill and used that to reinforce their primary skill. At first it was Java developers who had a solid grasp of things like CSS, but I also saw it in others who were working out product management skills or business pricing logic more related to finance than programming. These people also tended to make strong mentors. The people focused on only their primary skills weren’t as capable and didn’t seek mentoring themselves or have much to offer other junior developers.