We are aware that it's a pain to use just the data channel, and we're working on it. We're refactoring the native API to be more ORTC-like and make it possible to compile without all the audio/video parts. It will take time, but it should become easier as we make progress.
I disagree that the solution is to expose UDP API to the web. Writing good congestion control is very hard, and it would not be safe to let web apps do that; doubly so for crypto. As for native apps (even JS/node ones): you already have a UDP API.
The solution is to make the WebRTC API easier to use and simplify the protocol stack. We're working on the first, as I mentioned. And we're experimenting with the second (by using QUIC instead of SCTP+DTLS). Again, it will take time, but eventually we'll get there (probably).