So far it’s a nothing burger. Fired up a couple of Windows 7 machines with no problems.
Your Windows 7 machines will continue to work. They don’t suddenly go silent. But that doesn’t mean all is well.
The “screwed” part is mainly about the diminishing security, because as more Windows flaws are uncovered, they will only be fixed for Windows 10. The Bad Guys will know that those flaws are unfixed in Windows 7, so with a little “reverse engineering” of the Win10 security update, they will learn another way to attack Win7 machines.
Secondarily, over time, applications and accessories (Microsoft’s and third-parties’) will stop working on Win7, because updates and new releases will only work on Win10. Microsoft will go out of their way to make Win7 an orphan, by pressuring other manufacturers to make their produces incompatible with Win7. There is a long, sordid history of that happening in the last two decades, with each new Windows release.
So, in summary, enjoy it while it lasts.