The best replacement for webrtc is websockets.

The best alternatives to webrtc are rated as following:
★★★★★  websockets
★★★★★  sip
★★★★  xmpp
★★★★  rcs
★★★  cu-rtc-web
★★★  signalr
★★  rtmp
★  rtp
★  rtcweb

Your alternative for webrtc is not listed? Suggest!
Speaking about webrtc, one probably shouldn't forget about asterisk.

Other search terms related to webrtc and their ratings are:
★★★★★ asterisk
You have in mind a companion for webrtc and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of webrtc in all years. Click on graph for more.
webrtc
websockets
sip