To me these are clear security improvements; things are not getting worse. And there is absolutely no reason to think they'll be dropping support for endusers running their own compiled software.
The obvious end point would be the same as iOS, which is to say - you can run it to your heart's content, provided that you shell out for a dev certificate.
The fact that macOS is increasingly becoming iOS-like in both UX and approach to security is not obvious? It's pretty obvious to me from the past few macOS releases.
There are huge, important segments of the macOS user base that require the ability to compile and run their own applications, locally. macOS has pretty much taken over all of academic science & education, & personal workstations for government research. It is the default platform for developers of all kinds in Silicon Valley. As Steve Balmer once argued, it's developers that matter to the long-term health of a platform. Apple deftly captured that market by providing a beautiful and easy to use UNIX-like environment with high quality hardware and good design. If Apple locked down macOS the same way they lock down iOS, it would be the largest foot-gun in the history of computing.
Simultaneously, while the user interface of macOS has converged on iOS over the last half dozen releases and the ecosystems are more tightly integrated, not a single one of these changes has gotten in the way of developers running their own code. The situation now is no different than it was in 2006, for example. What has been made more difficult is running untrusted binaries downloaded from the internet. That's not the same thing.
One argument in favor of removing it (not saying it’s the reason or that they didn’t have other options) is that ctrl-click and open did not obviously do anything different. That is, whether you ctrl-click and open a signed app or an unsigned app, the command in the menu was just “open”, with no indication that you were overriding a security policy. Then the dialog it popped up wasn’t particularly distinct from the “first time run” dialog. There is an argument to be made that going to the security settings and specifically allowing an app is a more clear expression of intent. Kind of in the same way you probably want to open a file you download from the web, but good security practices means the browser doesn’t open it for you on download, you need to explicitly go do it.
That said there’s no reason they couldn’t have fixed either of those issues instead
