It's just a case of adapting to the conditions of the table. If you can't beat a sit out then something is wrong!
You just need to adjust your starting hand requirements and level of aggression by treating it like those players aren't even there. 4 sit-outs on a 10-handed game just means you (pretty much) should be playing 6-max strategy.
Remember though that in the early levels there is very little reason to be getting into a fight to steal the blinds!