It is definitely usable (my non tech wife and mom have done so for the past decade and it actually reduced the amount of support I had to provide for their computer in addition to giving a second life to a sluggish 3 years old Windows install that had almost convinced them to buy a new computer. As a result my wife's laptop is turning 12 this spring with just an upgrade to SSD 7 years ago).

The real reason why people [1] use Windows is that it comes pre-installed.

[1]: individuals, companies have other requirements and are tied to Windows for other reasons