What you're seeing are apps that aren't optimized for mobile. Once you start moving application logic, network IO, and anything that doesn't involve the DOM off the main rendering thread via a cached ServiceWorker, mobile web app performance jumps by an order of magnitude.

Every single performance issue that you're talking about can be seen in native apps; check Twitter, for example, or Facebook. There is a definite lag there caused by the network sync being front-and-center. That's unavoidable, but for an app like Vesper where you're not looking at a huge data transfer, running the sync in the background is absolutely viable.