I loved Blaze and closest thing to it is Ractive(https://ractive.js.org/). For backend reactive stuff there are many options like horizon/firebase/rapid.io/gun/etc, but for something more complex easiness of RPC through DDP is hard to replace though.

phoenix framework!

sure you may not get the oplog tailing but you do get a realtime websocket system that scales. Also, I'm fron teh school of thought that mongodb should never be your primary database for a whole host of reasons (no multi-record trabsactions, eventual instead of immediate consistency, limited query language to name a few). http://phoenixframework.org/blog/the-road-to-2-million-webso...

you don't get reactive stores (yet) but with absinthe's new subscriptions system, you can add in reactivity where it doesn't bottleneck your development.