It's no surprise that developers can self-manage the development of a source code tool. However this model is unlikely to work in any other space since the product requirements will not be in the domain expertise of the engineers. Github employees use the product all day in the process of developing it - this is true for hardly any products. Imagine engineers trying to self-manage the development of an ERP system - t…
Lots of great products are made by teams of only developers and designers all the time.
I think the real question is why do such low quality products get produced by business when building LOB apps to solve "real" customer problems. In my opinion it is too much interference in the communication chain between the customer and the devs designers and that is usually a management problem.