This is so familar! as you suggested in your closing remark in the past I’ve tried to find evidence of feature usage. Then I try and look at how that feature is being used, e.g.
does it really need to be surfaced in the UI anymore?
is this backend only?
What type of interactions “need” this feature?
I would then look to reduce the surface area of its appearance and gradually work it out. The theory being that if it is needed then it is easier to scale back up than re-introduce completely. One other side effect is that you get to question why the feature is needed, this might be different from the original introduction and you may learn a lot more about the product.
I‘;’ve had a couple of features where no one has noticed or asked me why they are missing . Another feature where it has been re-introduced is now a much more focussed sub-set of the original implementation.