Just a simple example: it's trivially easy to make large, flat shaded buttons on the web. That's going to be more familiar to younger users than native web buttons like those on HN.
However, there's also spending weeks to make a web button that animates smoothly from one container to another and has a SVG icon that morphs into another different icon with magic sparkles. Doing that on the web will require grossly perverting the DOM and all of the web interaction expectations.
A lot of the things we consider "Just 2016 App Things" are performances that native app builders have to do to give clients a reason to believe their $300/hour is well spent. No real value is produced except "design" awards for the shelf.