From Microsoft's FAQ: "Enforcement only happens on fresh installations, with Secure Boot on, and only applies to new kernel mode drivers"
In other words, disable secure boot and it's business as usual.
From my point of view, this increases security for the vast majority of users who just buy a computer in a store and need to be protected from themselves. If you don't know enough to disable secure boot, you probably have no business installing unsigned kernel mode drivers anyway. But if you do, you can.