If someone in Apple WWDR sees this, please take the feedback to heart and report it up the chain:
When you announce that a technology is being deprecated — such as CGDisplayStream — and also publish WWDC sessions about the intended replacement — ScreenCaptureKit — then you also need to give third-party developers a clear deadline by which this technology will be deprecated so that they can plan engineering efforts around implementing the new feature, and have ample time to communicate this to their customers. If it's important for third-party developers to get on board with this change, you should use every available means to communicate this to them, including multiple email alerts to their registered email address.
Additionally, if you plan to make a BREAKING change in a framework that results in a wildly different user experience, you should probably hold that off until the summer release for the next major OS.
What you should definitely NOT do is roll out a new privacy prompt in a mid-year release of macOS; or give your developers, customers, and AppleSeed program participants zero advance notice that this alert is coming, ignore your own Human Interface Guidelines when designing said prompt, and perform no user experience design testing (aka "putting on your customer hat") during a presumed internal alpha testing cycle to refine the experience and still find the most effective and least annoying way to present this additional prompt and spur change with your third-party developers.
Oh, wait, you've done exactly all those things the wrong way with respect to ScreenCaptureKit.
Right now, a host of Apple device administrators and client platform engineers are sending mountains of feedback to you, and they're also scrambling to contact third-party developers to let them know this is coming. Most of the vendors being discussed in private forums are said to be caught off guard by this change.
We anticipate that users are not going to like this, and there is no way we can manage it with MDM or configuration profiles. In short, the current experience is a ghastly mess. WE, the administrators, will get blamed for this, not the third-party developers. WE will have to explain to our leadership why this experience is terrible and cannot be managed.
Engineers need deadlines to help plan their work and prioritize tasks. In this case, vendors have had no firm deadline for this effort. There's already precedence for Apple announcing estimated deadlines for deprecations and feature removals. You do your developers and customers a great disservice by not communicating schedules to them.
Please do better.
P.S.: Feedback filed as FB13619326.