Doesn't have to be a Mac only app. But be considerate to your users and use the best available SDKs for each platform, not one size fits all.

If resources were infinite and there were never any trade-offs, most people would agree with you.

But what's your game plan under other circumstances? Do nothing?

If you're a small-time indie dev, do what works so that you can ship. If you're a well-funded co. like Spotify, GitHub, or Slack, however...

You're making the mistake of thinking that everything is just a technical challenge that you can throw money at, and that technical superiority is the only trade-off.

Just because an enterprise has funding doesn't mean it's wealthy in other, more scarce things like organizational capital. In fact, I wouldn't be surprised if all the client developers at Slack would love to split off into dedicated platform teams and do a rewrite. We as developers love that shit.

But you should try to understand why these enterprises make these trade-offs and why they are still in these positions in spite of how much disposable money you think they have.