I can see the use case for Qt5 and fink with Lazarus on Mac, but that would be a very small number of developers, perhaps vanishingly small, possibly only experienced developers with large apps who are comfortable with Qt and deploying and supporting Qt (ie, C++ developers). But that is not a solution for the rest of us.
The problem for Lazarus on Mac is not that it can't attract Mac users, but that it can't retain them. And can you blame these users? 32-bit Carbon? gdb? Are you kidding me? That should be the normal reaction to Lazarus. And a quick exit stage right. And that's exactly what happens. Just follow the postings and subsequent silence from new Mac users here.
I agree on the second paragraph, but there are more severe reasons than you give in the first paragraph. My point of view is, that the lcl itself has a number of shortcomings with respect to macOS and violations of the Human Interface Guidelines, independent of its basis, whereas the extra layer of the lcl actually prevents you to deal with subtleties of Qt, at least from most of them. The problem with gdb is also independent of the lcl basis. The point I want to stress is that if the carbon-based lcl was good enough for you so far, chances are good that you can get along for example with the Qt-based lcl. That is what i meant with no reason for despair if the support for carbon stops. The end of lazarus-carbon does simply not put an absolute end to lazarus on macOS. Even if lazarus-cocoa has not reached a sufficient level. Sure enough, without lazarus-carbon the situation becomes even worse on macOS, but lazarus-gtk2 and lazarus-qt4 are already available as fink packages and can be used, although i haven't tested them extensively. As soon as lazarus-cocoa is possible as a release, i will put it together, even if it needs some patches. I'll give lazarus-qt5 a try with version 1.8.0.
I have the impression that when it comes to macOS, people limit their view to the carbon-based lcl and miss all other options.
MiSchi