I know I'm super late to this and firstly, I hope you're okay

mental health is a struggle especially for a subject like English which can be so demotivating
I do advanced and used to do extension so my opinion is definitely skewed, but here is my honest opinion
Standard is less work. I know many people who dropped and half of them say it's the best decision they ever made because of how little effort they put in compared to adv (they're topping the course after dropping).
On the other hand, my school averages like 10-20 b6s for adv a year and gets almost no b6s for standard. One of my closest friends really regrets dropping adv bc, in their words, "the content is basically the same but for worse scaling". Scaling is a bit of a taboo topic which I totally understand but in year 12 they sometimes talk to you about it (which imo is a bit late, but whatever). Also, just consider the texts - some people love Shakespeare and hate modern texts, or vice versa. How much you like a text will significantly affect your willingness to study, so maybe ask some older kids what texts they're doing.
Idk how scary ur teacher is, but worst comes to worst, just go higher up the ladder - complain to the head of department, or ur cohort or learning leader or whatever they're called
I understand getting subpar marks is really demotivating - I completely understand it when you feel like you're not reaching your goal and feel like you won't be able to - but all it takes is one breakthrough and then you'll be able to slowly push your rank and marks higher and higher! And you always have this site to help you if you have any questions
Honestly though, do whatever stresses you less, if adv is scary then the relief you get from dropping will probably lift your other subjects anyways and erase any potential loss of ATAR