Just to add, Vista’s biggest change broke compatibility with so many applications with the implementation of User Access Control (UAC).

While it was a long-overdue feature for security, lots of older applications would either fail to install or not work properly because it expected to have full system access with no roadblocks. While there was compatibility mode, the results were still very much hit or miss.

Then there was the massive headache around the original implementation of UAC which would constantly go off, usually multiple times during a software installation and again when starting some applications. Most people would’ve turned off UAC because of how annoying it was.