"But how to 'be yourself' if you actively don't like who you are?"

I asked myself that question a lot in my teens, lost in naivete, thinking that if being yourself doesn't work, the solution must lie in the opposite.

But you're right: you can't be someone else. So the solution is not to fake and hide, but to grow and thrive. Polish what's already there, learn about your interests, become good at what fascinates you.

To be "more yourself." That's the solution.