For those American soldier in Iraq/Syria,what is it actually like fighting againts ISIS especially in 2014 (peak of ISIS),furthermore why didnt America go on all assault on ISIS ?

Is ISIS like how they portray it in the media in 2014 ? Unstoppable,vicious,super battle tactics,etc or is it exaggerated ?

During the peak of ISIS 2014,why dont the allied force fight ISIS as how they actually want it to be defeated,is interest at play here ?,According to Google Isis had only like 30K-40K fighters...so why?? it is as if the countries fighting againts ISIS is not actually interested in defeating them but containing them...im not a military/geopolitic expert so what do i know