Completely disagree. We started using Firebase; compared to using websockets with e.g Pusher its much, much simpler, primarily because it's a store of state as well as a real time stream. It also handles going off-line and then syncing whilst coming back online perfectly and without any additional code.

Yes of course you need a server for most apps, but I don't see a problem with that. Yes, your app might have data in two places, but it's still the simplest way to build a real-time app. My biz has done it several times and the smallest, simplest code base has been with Firebase. Far fewer moving parts too.