Their charm is BECAUSE they are so basic - no pretence - a mass produced vehicle that everyone could afford - the beetle, or a commercial load carrying vehicle - the Kombi which evolved into a people mover then a holiday mobile home. All the problems that you mention are true, although in later years, the bay window kombis (single piece windscreen) are more driveable - if the stars are aligned and everything connected properly, my heater works and the disc brakes are fine.
The iconic kombi is the early split screen version and it is guilty as charged however last year one sold in the US for in excess of $200K. In Australia, a restored "splitty" sells for north of $60K
Everytime I drive mine I have a smile on my face - its that sort of vehicle; as I do when I drive our pagoda, but this is more of a giggle.......... You sit nice and high so its a great view - lets you see around all the pretenders in their SUVs and you can imagine you are driving a Mack truck with the upright seat and flat steering wheel. For many people, they evoke memories of their youth; for some a hippie lifestyle, for others of time spent camping or living a surfing life, or for others a pretence that that's the life they are leading now.
They can be a challenge to drive; not known for their power, and equipped with an automatic, unannounced lane changing capability in strong cross winds just adds to their charm, as does a gear stick with worn linkeages - its a couple of metres back to the gearbox - and gives the stirring porridge impression.
All in all a fun car to drive that nobody takes too seriously-well that's not completely true, we do have the types that rabbit on about whats genuine of not - what color cad plating the bolts should be that hold the tin ware to the engine bay etc etc, but they are in a minority. Most people just want to enjoy their kombi.
cheers
George