Again, you're judging it by a standard that open development models don't work by. Many open projects started out with a level of quality comparable to this and go on to drastically improve as the development process goes on.
Unlike in proprietary software land where they already have paid developers these types of open projects release much earlier in the process often in the hopes of attracting further contributors and not really having customers that they need to impress by waiting for a more polished first impression.
It's just not a comparable situation to how other games are made.