Do people really know all this stuff or do they know like 25% of it and get lucky where the interviewer ask the 25% they know? I have been doing data work for

Do people really know all this stuff or do they know like 25% of it and get lucky where the interviewer ask the 25% they know? I have been doing data work for 3 years and software for 3 years before that and I only know less then 25% of this. I have probably learned less the 10% of this on the job.