I've used Linux over the years. But a niche desktop environment being better in some very specific use cases isn't much of an argument.

Why not? People choose their tools by criteria that matter to their use cases. For some, alt-tab behavior doesn't matter. For others it's a primary pain point.

Computing should be personal. Some people like to mold their tools to their way of working. Others adapt their way of working to their tools. KDE is for the former, and macOS is for the latter.

Why would someone else use my criteria? They should use their own criteria? I certainly am not going to use your "it's niche so it can't be useful" criteria as it's important to my usage.