'Closer to irrelevant' is a bold statement to say. Windows is strong, not as strong as in the 90's where it was the only consumer oriented OS, but is far, far away from being 'irrelevant'.
For a more direct comparison Windows phone has 5% of iOS market share and 1% of Androids. Most major software news is off Windows Instagram and Pokemon Go for example really don't care about the desktop. The web got good enough that many services are native on mobile and Windoes just gets a website.