[MaknMoreGtnLess]

You need to know what you need to improve on and your manager can share that with you.

You need to be honest with him/her/them, tell him you know about the promotion and that you need him to tell you where you can improve on. It's perfectly ok if he doesn't think he will ever promote you - you just need honest feedback.

The other way is to try and interview elsewhere and hope they can tell you what you need to improve on.

Another option is to look for career coaches. I often interview candidates who are preparing to interview at FAANG through a network but it's in the U.S.