I actually just completed an iOS course. I think that it's good to know how things are done, and there are some things that you'll want to do completely native. (Such as complex graphics). But the iOS interface building tools are utter crap compared the JS/HTML ecosystem. I would say, build a few small apps completely native, just to see what you're not missing out on and be ready to write swift or objc to do really complex or performance critical things.