The future of macOS development may be SwiftUI, but that's also the future of iOS, iPadOS, watchOS, and tvOS development.
But I think you're right. Catalyst (née Marzipan) is being pitched by Apple as a brilliant way to get a head start on porting iPad apps to the Mac, and should become the best way to write an app that you want both an iPad and Mac version of. But "Mac apps as we know them are dead" always struck me as histrionic, and today's presentation doesn't make me think that any less.
But I think you're right. Catalyst (née Marzipan) is being pitched by Apple as a brilliant way to get a head start on porting iPad apps to the Mac, and should become the best way to write an app that you want both an iPad and Mac version of. But "Mac apps as we know them are dead" always struck me as histrionic, and today's presentation doesn't make me think that any less.