I don`t think the importance of a mentor has gone away or changed, the amount of real leaders than can mentor has declined significantly though.
You can call it what you want, a mentor, a role model, a leader you are inspired by, they are very important. It can give you years of knowledge and experience with out the years of trial and error, mistakes. If you want to do XYZ and you find somebody who has spent their whole life mastering XYZ, of course it is better to study that person instead of studying XYZ.
I have different mentors for different areas of life. Its also important to learn that you too can/are a mentor to others. You have kids? Your a mentor and you better try to be good at it!