Nowadays Windows is filled with adware and is fairly slow, but it wasn’t always like this. Was there a particular time where a change occurred?
Windows is far from being free. Buy a laptop, you also automatically buy a license for windows, typically about $100. Build your own computer, need to pay for a license as well. They just hide the cost a bit, but you still need to pay all the same.
I think what they reference is that it is free to upgrade. You could upgrade 7 to 10 and 10 to 11 for free, used to be you have to buy a new one. Now you have one time entry fee to the ecosysyem and then they keep you (though they sidestepped this with some system requirements for Win 11 now)