It depends upon whom you ask. In a general we can all be better than we are at something, so in that sense we are sinners. In the context of 1John 1:9 a person should consider themselves a sinner compared to God in terms of truth and importance with no extra levels between any two people. Confessing you are a sinner is admitting there is no right person to ask questions of, nobody whose ideas are above another's ideas. In the original (I suggest) context this verse goes so far as to equate people of different intellectual strengths, backgrounds and perhaps even undermines the right to own claim property, though that is unclear. Romans 3:23 says "All have sinned" and moving towards verse 27 adds "where, then, is boasting?" We have James 2, too, who says not to show any favoritism, to love your neighbor as much as you love yourself, not to boast, to accept that wisdom comes equally to all from God. The ones who don't accept this it calls double minded (division minded?). James 3:17 says " But the wisdom that comes from heaven is..impartial and sincere," contrasting it with the wisdom that comes through people.