The Forbes article is a tad hysterical in tone, to say the least. And some of it verges on the inaccurate.
1. What's with the headline? Nonsensical...
2. As Jim notes - Apple has been warning of the demise of 32-bit support for 10 years now. This is no surprise.
3. Overdrive? Really? Who the heck uses Overdrive on a Mac? If you're using it to read library books (the most popular use) you are almost certainly using it on an iPad or iPhone. Not a Mac. Talk about picking a rare use case.
4. Dragthing? Hasn't been updated in three years. There are alternatives. (Station, for instance). If it was truly THAT popular, then the developer would have incentive to update it - but it's not, and so he's moved on.
5. Microsoft Office? Um...yeah, Office 2011 won't work any more. It was released Oct. 26, 2010. That's NINE YEARS ago. Office 2016 received updates to make it 64-bit compatible. So yeah, occasionally you DO have to upgrade your software if you upgrade the OS. You know...every decade or so.
Of far more concern are the things that
should work but have some serious glitches - ie: Adobe's online apps. However, I would expect those things to be fixed pretty quickly. And in a production environment, most people don't live on the bleeding edge either, waiting to update until the initial bugs and issues are sorted.