What blows my mind is that there's a Rust encoder, but no Rust decoder. There are many more orders of magnitude of people who will use a decoder than an encoder. One would think that the safe decoder would have come first.
By focusing on an encoder (at least initially) you can just support a subset of features that work well for you. Then focus on making a decoder that can at least play back videos from your encoder.
More people will find it useful to have an encoder that works all the time, rather than a decoder that only works on a subset of videos.