Want easy object-orientation? Use backbone. More of a functional programmer? There’s underscore, lodash and many others. And I can’t keep up with the latest template rendering libraries, but there are dozens.
Plus ECMAscript 6 is rolling out quickly and with it, some long-awaited language features, syntactic sugar and new APIs.
Additionally, there are a lot of JS SDKs and simple integrations for things like accepting payments (stripe), analytics (mixpanel, customer.io, etc) if you don’t want to write the code or support the infrastructure to do those things yourself.
Do we even need to deal with setting up servers and maintaing a separate codebase for a server-side backend at all?