i don't see SOR roaring moon being significantly harder to deal with than others you mentioned for reasons threefold.
1- it's reliant on contact moves. this not only leaves it walled by common Fluffy sets (notably Corviknight and Great Tusk) but also opens it up to being situationally
easier to chip than something like chien-pao with rocky helmet, flame body etc. being punishing.
2- knock off is broken, but only when you have a strong secondary stab to make up for its downsides. urshifu and weavile are genuinely broken pokemon that can spam knock off in the early game and still break with close combat or triple axel respectively later on. roaring moon in contrast has to choose between: outrage, a move that locks you in for 2-3 turns and can secure your death. knock off, a move that is 65bp on a second hit, and a handful of significantly weaker moves like crunch and scale shot.
3- it doesnt actually have a lot of abilities to prep for.
this is a bad comparison because lele's 2-3 sets demanded wildly different approaches with triage nullifying offensive counterplay while sflo and tinted lens shredded defensive counterplay. to answer roaring moon you need a pokemon that can switch into knock off and that's about it because nothing between sword of ruin, adaptability, magic guard or regenerator lets it break through dark resists any easier - there is no roaring moon that beats fluffy corviknight or regenerator primarina without sacrificing all of its strengths to do so (i think it was
Giagantic running that awful mixed fire blast moon? shoutout deserved). yes, maybe you'll be punished if you don't scout choice scarf, but that can happen with every offensive pokemon and it doesn't mean it's broken. it's extremely easy to play around with a well built team.
i'm a firm believer in magic guard being the best ability for roaring moon because it takes advantage of roaring moon's solid defensive profile to switch into pecharunt, iron moth etc. and removes some of the defensive counterplay i mentioned earlier (hazards and helmet). it
can break past pokemon like corviknight given enough turns and support to do so but that's because it's a top tier pokemon and it rewards you for playing smartly with it.
the banpost can be found
here and it was so long ago that not all the reasoning will be relevant anymore, but the short answer is secret sword is very similar to psyshock and lets it break past most specially defensive walls with ease while belonging to a notably stronger offensive type. it also ran tinted lens quite a lot, which in the current meta would let it do things like this:
252 SpA Choice Specs Tinted Lens Keldeo Secret Sword vs. 0 HP / 0 Def Iron Moth: 312-368 (103.6 - 122.2%) -- guaranteed OHKO
a strong hydro pump would help it burst through traditional fighting type resists like pecharunt, and while you could definitely answer it with techs like water absorb pecharunt, defensive latias etc. the tier is better without it around.