”My question is, are there any societies where the adult children continue to live at home but ARE NOT EXPECTED TO contribute to the household or contribute to society in some meaningful way? Can you shake your righteous assumptions and prejudice long enough to see the question as I am actually asking it?”
Different cultures and different families and different people do have different ideas about the sorts of things you seem very attached to framing in one very judgemental way.
For example, what people value as counting as contributing to a household and/or society in a meaningful way, depends entirely as what people define as being a valuable/meaningful contribution.
Many cultures have a history (including some of the USA within living memory) of expecting female children to remain at home until married, with their contribution being making themselves attractive marriage partners and doing housework, but not being expected to support themselves (in fact, that might be seen as unrespectable).
Also, many people are not preoccupied with the worry you mention, and have other frameworks of ideas about their children and other family members, for example where they would love to continue living near them and for them to do what they want with their lives, and take joy in providing helpful circumstances that contribute to that.
I know quite a few parents and grandparents even in the USA who have expressed welcome to their children and grandchildren to stay with them if/when they need/want, without shaming them if they aren’t actively pursuing jobs or paying/earning “their keep”, or even concerning themselves with any such notions.
And certainly there are conditions where even “pull yer weight” Americans relent in their shaming of non-working house guests (e.g. disabilities, illness, divorce recovery). So why would no one tolerate other less obvious causes of lack of will to work at McDonalds?
Some cultures, families and people even respect non-financially-abundant choices of profession, even art, music, writing, philosophy, or mysticism. Some respect those far more than earning money.
Surely there are many examples (especially in the USA) that match your pattern… but many of them may also tend to be at least partly caused and perpetuated by that pattern. What you resist, persists. A parent who expects and/or fears that their child may become a stay-at-home mooching deadbeat, may tend to load those children with stress and resentment and regenerate those stories and that behavior and that type of relationship for the next generation.