We're not far off but 3 main reasons;
1. We're not clinical enough.
2. Our mentality.
3. We don't have an x factor player in midfield like a Silva, Ozil or Hazard.
None of that means we can't win the league - it makes it unlikely but mentality/clinical finishing can/will hopefully improve with time and maybe someone like Eriksen can step up and be our X factor midfield player? He outperformed Ozil in the second half of last season iirc (creativity wise)
Last season it was our (relatively) poor start to the season which let us down - I think we beat Leicester for points from about match day ten or something and this year we have started much better, if we hit our stride then anything is possible