It is kind of true though, that the modders have made more for the game than his own people have. And the game is artist light, it is quite easy to mass produce a lot of art for it and introduce new things. Also the Creative mode is something I still very much so miss. I got bored having to first spend hours before I can finally get creative. It is like having to take your bike to some distant toy shop and cycle for 4 hours every time you want to play with your legos.
He also sold a lot of copies while it was in alpha, and if you sell an alpha product you kind of make a promise to people that there are going to be a lot of updates in the future. It is still alpha after all, so that means a lot more is to follow. That is the downside of this whole "fund my under development game" approach, people get expectations, and people get a sense that because they funded development, which is what they essentially did, they can demand and expect things to happen. It is also a bit of buying a cat in a bag. You don't really know what you are actually buying since the product is still evolving, further adding to the frustration. If you buy a finished game you know what you are getting. It is pretty much like giving a presentation. If you present some game concept and you only show an actual demo of the game all the way at the end of your presentation, people are going to be disappointed. Because by the time you got to the end of your presentation, they will have already developed their own view of the product, and your vision is never going to fit the version they've constructed in their own imagination. You really can't win that fight.