I just disagree, for me and my group. We (my group) work on house-rules together, it is not all on me (the DM). Also, the meat of our house-rules are something that most people don't want. We don't have any issue with or need to fill the "foreseeable gaps & self inflicted problems" that you see (most likely). I think that is precisely why it a good idea to let the 3PP handle it. Now. I would have any issue with WotC release supplements that variant and additional rules. However, I don't need WotC to do that, i am perfectly fine with the 3PP market providing those. To me, that is no different than WotC providing them.