The More Things Change ...

Once upon a time (& yes, I'm old enough to think of my earlier career as possibly mythical), we used to talk about "cross-browser" issues. Let's say around the year 2000, when the three major browsers were IE (which was getting behind in functionality), Netscape, & anything you could get to run on the Mac. At the time, it almost didn't matter what the browser was on the Mac, as long as you could demonstrate something.

The problem then was that there were lots of different implementations of the HTML standard & interpretations of how it fundamentally worked. There were also a lot of extensions that made HTML useful. It usually meant that you could not, under any circumstances, release a web site unless you either specified the browser (which meant you were stuck on an older version of IE), or else had tested on several versions of several browsers.

Then some **** (company) would release a new browser version just as you reached go-live for your website & marketing campaign, & you had to start testing all over again.

Those days were almost over when HTML5 started coming into the light. I think that we're not only back at square one, but we're worse off with Firefox & Chrome now major contenders in the browser market, but at least you're less likely to do much that's specifically targeted at the Mac - unless you want to.

What really becomes the problem is the cross-platform issues around phones, tablets, phablets, notebooks, airbooks, laptops, & any of a number of variations on the theme, with their different browser implementation engines, screen sizes & resolutions, aspect ratios, etc.

This nightmare just gets worse if you are responsible for launching a web site that caters for desktop & mobile, or else a multi-platform app.

Into this market come the cross-platform development solutions & multi-platform deployment solutions. The former let you build things that can be converted into native apps, while the latter let you build things for an indeterminate infrastructure (like a VM) that can be run on various devices.

This does not solve the problem, but it does make the development easier. Rather than trying to develop multiple solutions - often independently (different developers in different dev envs) - you develop the solution once, as a designer, & then hand this over to an integration/deployment specialist who just has to tweak the application to run on whatever platforms are needed.
Then you click the heels of your red slippers three times ...

This process changes the structure of the dev team. You end up with UX people working hand in hand with DevOps types. You often have platform-based non-technical testers at the end.
This is very different from the traditional position of having devs doing almost everything, & devs who work as testers doing the QA.

If you take the right approach, cross-platform development for mobile applications these days is not as bewildering as it at first seems, but it can't be done by just transferring existing dev models to new technologies.

However, if you don't change your ways, you will be stuck with the same problems that we had at the turn of the millenium.