RFC490 was simply a "rollup" of SCTP at that point with minor corrections not some protocol with immaculate birth where the initial RFC gets you up to date with the protocol. It also features a large set of errata and about a dozen feature extension RFCs that have come out since (as well as an RFC on security attacks found against SCTP that one definitely should to read before writing an implementation). I'm also not familiar with any recent protocol added to browsers that has been abandoned from a standards perspective in the way you describe. Websockets and what were known as SPDY & Quic have more standards activity than ever before.

Are you referring to the barrier to use WebRTC or the barrier to make your own implementation?