I agree, when deciding on footway / sidewalk I always imagine typical use case: a young thin mother pushing baby pram with twins inside. Would she be able to safely use it? If yes, then it is highway=footway or sidewalk=yes etc.
If not, then it is not footway, but highway=path + wheelchair=no + sac_scale=demanding_mountain_hiking (and maybe even alpine_hiking if judging by some parts on that picture when usage of hands is required to proceed using that “sidewalk”).
See also somewhat related How to tag *unusable* sidewalks?