With English – you either have it or you don’t.
All 3 of my children have been in gifted and talented programs, and the oldest 2 (both now out of school) excelled at English and did extension English. Both achieved excellent results. My youngest is now in year 12 and – while he is undoubtedly the smartest of the 3 overall – English is completely alien to him. He topped the year in other subjects – but analysing poetry and interpreting novels just defy him. And, as you say, that affects the ATAR and there is no way around that. As English is the only compulsory HSC subject, it is an inescapable nightmare for those who aren’t inclined that way. (And when the English teacher – who is also Head Teacher of Student Welfare – happily tells her students that she hates all males because her ex-husband was a jerk, then the nightmare escalates to an epic, insurmountable horror, and you can end up with a young person who spends their time contemplating ways to kill themselves and under the care of a pyschiatrist and psychologist).