Microsoft's continued slide into irrelevance
This article seems to gloss over Microsoft's irrelevance in the only growing market: mobile devices. It acknowledges that browser development is expensive but fails to take this into account regarding Microsoft's attempts.
It has been force-feeding "Edge" on Windows 10 users for years now and it's still only getting 2-3 % of desktop users, itself a shrinking slice of the pie. Enterprise users were badly burnt by the "seamless" integration via ActiveX of IE and, because, Microsoft was so slow to devote resources to web compatibility, they specifically targeted web compatibility for the next generation of network-based apps, not leased because corporates are mainly still on Windows 7, so all the Edge "goodness" isn't available. Enterprise apps have lifecycles of at least 5 years.
Microsoft has had to recognise its failure by releasing Office for Android and IOS, once it realised that people would happily pay for it.
Back to Microsoft's browsers: IE 9 did include a significant rewrite of the renderer but IE 9 - 11 were hamstrung by all that ActiveX compatibility. Edge has dropped this, but as the CERT reports show, still share enough code with the older versions to be vulnerable to many attacks. It's now playing catch up for features but, as so often with Microsoft, you can never be sure it will continue to devote sufficient resources to the project. Fortunately for them, it looks like most of the stuff that was missing from HTML has now been added and a more gradual development path is possible.
The debt we owe to those at Mozilla and Opera and later Google who fought for open standards cannot be understated. Without it we'd still be developing browser-specific sites and be dependent upon shit like ActiveX and Flash for advanced interactivity. Anything that smells like that kind of lock-in is not going to get a look-in for the next few years.