#1 is you.
You have the skills to do the work that has value and impact. You have the capacity to grow so that you can take on more responsibility. With increased responsibility for people and projects, you can have greater impact on the product, the team, and the company.
#2 is your manager
Your manager helps you identify the skills that you'll need to have impact on this team and project. Your manager reveals to you blindspots, hidden potential, and areas where you can grow your skillset, toolset, and mindset. Your manager coaches you to get you past blockers and friction slowing your growth and impact
If not the 2 of you then who? Right?