I'd argue that google is pretty strong when it comes to frameworks, and that most of their criticism comes from people who aren't looking for a framework, but rather a library (like React).
And Polymer isn't even really either of those things, it's a polyfill for a native browser feature.
Polymer is not a polyfill for web components - it is higher level library - something like "jquery for web components" - WC polyfill is separate project, in separate repo - you will need it with X-Tags, Svelte, SkateJS too.
And Polymer isn't even really either of those things, it's a polyfill for a native browser feature.