Why should a real estate asset that does not appreciate in value continue to exist? Assets that don't appreciate in value can be demolished and replaced with assets that do appreciate in value. Assets that appreciate in value have an intrinsic reason to continue to exist; assets that depreciate in value don't have to continue existing. (And yes of course an asset that is depreciating in value should continue to exist if it is being lived in)
Existing housing appreciating in value also does not prevent new housing from being built. If every house is going up in value a little bit each year, an investment-minded person might see this and say "hey, I should build a house, as it will appreciate in value". Once housing -stops- appreciating in value in an area, people stop building additional housing in that area. So appreciation tends to spur construction until the appreciation stops. People don't build additional housing in areas where housing is depreciating in value, so on the average, construction should not be expected to halt appreciation, since appreciation encourages construction specifically in areas where appreciation is likely, and not in areas where appreciation is unlikely.
There are many similar effects that lead to appreciation in value on the average. It's not clear why housing appreciating in value should suggest that "we're getting significantly worse at producing housing/shelter".