Webpages don't work offline. All the user has to do to break everything is hit "refresh". What your business users wanted was an app, and you gave them a webpage instead.
I also don't understand why you would do rendering both server and client side. That's an overcomplicated architecture that doesn't buy you anything. If you chose one, you'd have a simpler architecture.
And before you claim "optimization"--did you profile?
1. Hitting refresh doesn't break everything. It resets your current state to the default. I default to the url combined with locally stored state, so you will lose text in an input field, but not much else.
2. I want a website not an app, thank you very much. I'm really just displaying text. I don't need to download an app for that when I have a perfectly good browser on every device I'd like to read from.
3. Maybe it's over complicated to you, but the same function that renders on the server is what I use to render on the client. Zero difference. It's not a choice I have to make so I can use either when I feel it's appropriate.
Really?
1. Go to your website.
2. Disconnect from the internet.
3. Hit Ctrl+Shift+R.
How's that app you wrote as a website working for you?
It's called appcache. Works in most browsers. You should look it up ;)