Polymer is greatly undervalued. I takes a bit of time to get into it but once you understand all the quirks, it's smooth sailing.
I really like the simplicity of it.
React is good too, but you need the right framework on top of it (or else it can be a bit tricky to setup properly).
React is good too, but you need the right framework on top of it (or else it can be a bit tricky to setup properly).