This is not a question. It is an assertion. Similar to many other assertions you have made in which you equate voluntary social isolation with pathology.
so let's explore your ideas.
hoarders tend to isolate themselves - yes. But I would say "most hoarders"
they seem to think that stuff will keep them company - perhaps, I have never met a hoarder who expressed that opinion. Have you? I have met many who prefer interacting with objects or animals to interacting with people. I consider that a valid preference. Some people want a job at the reception desk. Others would rather process orders alone from home.
what it really does is builds [sic] a wall between them and their family friends and community - in some cases this is done deliberately - I build this wall to keep you at bay - not the optimal solution, I would agree. When that wall is unwanted, then the wall is the problem. When the wall is a coping solution to another problem, then you need to step back and address *that* problem. If I turn my guest room into a storage unit because I want to keep the stuff and I don't want anybody to come visit, I'm not sure there is really a problem. Is there a problem if I get a smaller place because I don't want visitors to stay with me and just rent a small storage unit? An actual problem, not a conflict with your personal beliefs.
it really is a sad state to be in - "it" in this case appears to refer back to social isolation. If the person feels they have adequate human contact, why is it sad?