But the fact that it hid it until someone finally tried it on a device is the simulator's fault.
The same thing would happen if you'd tested on an iPhone 5S and then your users tried to run it on an iPhone 4. Is that their fault also?
And you've never had websites that did anything even somewhat complicated in JavaScript, huh? Since you aren't allowed to run interpreted code on iOS, it had to be redone in Objective-C, and the initial version turned out to be very slow. (Think "charting.")
Odd to hear this from you, since we deploy many apps written extensively in JavaScript, but do go on.
I mean, sure, we could have just embedded a webpage and done it that way, but the existing JavaScript was already unacceptably slow or we wouldn't be looking at making an iOS app, now, would we?
Aha! Sounds like you had slow code in one language and replaced it with slow code in another language. FWIW, there are plenty of free JS charting libraries that run really well generating complex charts blindingly fast even on very old iOS devices.
What's that saying about a craftsman blaming his tools again?