I feel like it's not only certs that are retiring, most MS dev/sysadmin I know (myself included as MCSA) have moved to linux stacks in the past 3 years
There is an ever increasing number of Linux servers, that is correct, but there is still a huge base of personal PC's (laptops, desktops) running Windows in Active Directory in many companies; there is still specialized software that runs only on Windows even on servers - I know in the area I work the top options are Windows only - so there is still need for Windows admins.