NAT traversal is part of ICE, but another part is formally specifying things like how to trigger accepting a connection, and which connection can be tied to which WebRTC session. This can actually make it easier, not harder, to use WebRTC.
In addition, the SDP exchange also sets up DTLS, making sure that whoever the WebRTC SDP was exchanged with is the same as whoever connects at a low-level. While you can implement this as a messaging exchange over UDP once the connection is established, its a nice property that WebRTC doesn't even allow the connection to be established with a non-secured link.
I think the hardest part of the stack is getting a decent, stand-alone implementation. With things like Websockets creating a server is straightforward, but libraries for low-level webrtc are much harder to build.
In addition, the SDP exchange also sets up DTLS, making sure that whoever the WebRTC SDP was exchanged with is the same as whoever connects at a low-level. While you can implement this as a messaging exchange over UDP once the connection is established, its a nice property that WebRTC doesn't even allow the connection to be established with a non-secured link.
I think the hardest part of the stack is getting a decent, stand-alone implementation. With things like Websockets creating a server is straightforward, but libraries for low-level webrtc are much harder to build.