There's been a longstanding issue that a lot of people are unhappy with the level of control that Evan exercises over the development of the language. On top of that, a lot of the development of the core language happens behind closed doors, which has given the impression of stagnation over the past few years.
As I understand it, the fundamental reason for this situation is technical. It is really difficult to enforce purity in a strict language with an FFI, because the behavior of side-effecting functions would be predictable and they'd be easy to use. In contrast, while someone certainly could release a Haskell library that made pervasive use of side-effecting functions, the resulting library would be horribly brittle and no-one would want to use it.
Evan really wants Elm to be pure. To ensure it stays that way, he's banned community packages from using the Javascript FFI. This has been unpopular, but I think he's probably right that this is the only way of keeping the language pure.
It comes back to the usual open source entitlement debate. A lot of people seem to really deeply believe that Evan owes them something, and is required to manage his project along the lines of some kind of standard 'open source' model. He doesn't see it that way.