"decreases hit circle size by 1 tick while increasing the overall difficulty, approach rate, and the HP drain by 2 or 3 ticks of their original value up to a maximum of 10. [...] Additionally, this mod flips the map on the X axis, so that elements that were at the bottom of the map are now at the top and vice versa."
take the hp drain away. now is it possible that increasing the overall difficulty makes it easier in any way for you? no. take that away too. so what's left?
- smaller circle size.
this map has it's hitcircles and sliders rather close to each other. hr gives it a more spaced feeling by decreasing the circle size.> maybe you need training in reading stuff like that? like playing more technical maps?
https://osu.ppy.sh/b/963412https://osu.ppy.sh/b/859001- approach rate
many people have difficulties reading lower approach rates. mostly it's about people who can't read <ar8 but play perfectly fine on ar9+. maybe you just have a more extreme version going on and would be fine playing something like ar9,5 or even ar10. idk. i don't have a low sr ar10 map but here's some 9,4. try it. the map is harder than stella-rium but maybe you'll feel that the higher ar is better for you. if so then i'd definitely recommend you playing more lower ar maps because you definitely should be able to play at almost any given ar. just train. and stop playing so much dt + hr since it raises the ar artificially.
https://osu.ppy.sh/b/864246- flips the map
i don't think this would change anything. idk. maybe you played it more often with hr and memorized it so that nomod seems unfamiliar to you and you're worse at it. could be the case idk.
anyway. you're playing maps way over your skill level. take a step back before trying to take the next one. this is just advice in case this happens to you at other maps too.