This is a solved problem via service workers. They can cache all the app's content and you can choose to cache whatever you like including api responses from any service. They could also be configured to serve cache first and replace the content in background. At this point if the app is slow to start, it's 100% on devs/architecture. The only problem is if you exceed the quota for cache, which is varied by browser/platform, you risk the browser just nuking all your cache/localstorage/indexeddb.
Yeah, GCP is not the same as Google Reader, more like Google Maps. But that one recently had some changes that royally fucked some businesses over by changing pricing and quotas, so maybe not so absurd after all.
It's not insane. FYI the fastest terminal (alacritty) achieves its performance by rendering via gpu, and it's written in rust. iTerm recently started doing it too.