If you target desktop, should be fine, but mobile users tend to use cell towers which are on Symmetric NAT, which would require a TURN server on top of the WebRTC.
Even on desktop you run into people with weird configs. For example my router will not allow mDNS to work but my ISP NAT is pretty good so I can connect two machines as long as they’re not on the same network! In the end you almost always will need a relay to guarantee connectivity for any random pairing of participants in a large enough population.
The good news is that WebRTC is perfectly straightforward if all you want to do is to connect to a server on the open internet.
