Periodically I hear from people at EA organizations who are experiencing imposter syndrome or other anxiety about how well they're performing at work, especially when starting a new role. I wrote up two guides on this, one for interns/new staff and one for their managers.
Guide to welcoming interns (for managers)
Countering imposter syndrome and anxiety about work (for new staff and interns)
I think the first step, if you believe you're less competent than your colleagues believe you to be, is to find out who's wrong—you, them, or both? And are you wrong about your assessment of yourself, or about what your colleagues think of you, or both? Think about what questions you could ask or what metrics you could measure to answer these questions.
If it's your colleagues who's wrong, is it worth correcting them? They understand the risks, they know that recruitment is hit and miss. Is it your responsibility to protect them? You can live in fear of the moment when you'll be found out, or you can cherish the days when you are allowed to do the job, and accept your fate with equanimity. You're not getting your head cut off; you can choose how you feel about this.