From top of my head:

File renaming. What Forklift or other dedicated file renamer comes as a standard with both Dolphin and KRename. Latter can drive circles around what's available in macOS, in any form.

AudioCD ripping: kio:// protocol has a native ripper. Just drag and drop. Settings are integrated to system settings directly. Which format do you want? Yes.

Remote connections: While finder can connect to servers, but FTP read access and SFTP requires external apps. IOW, what Cyberduck provides is already available in Dolphin, again.

KDE's standard window management capabilities need Magnet or something more advanced in macOS.

Git/SVN/CVS needs external tools in macOS. Dolphin can detect these repositories and let you work on them on the spot.

KRunner is arguably more Capable than spotlight in some cases. Needs another fair shake though.

If you add your mail accounts and calendars to KDE via KMail or something else, they become available system-wide. macOS is good in that regard, but KDE is betterer. If you use KMail, your mail will sync at the background even though your mail client is not running.

You need to buy another application to be able to edit id3 tags of audio files, but KDE has kid3. I even use its macOS version because it's that good.

I'll not get into customization capabilities, because they are fundamentally different and worlds apart, but this is due to their philosophy.

Keyboard shortcut management are equally powerful in both, AFAICS. macOS used to lag there.

K3b is infinitely more capable than macOS optical media authoring tools.

These are what I can remember with my tired brain, away from my KDE system for the day. The thing is, both side by side, I mostly prefer KDE because I can work way faster on that one, and it's not I'm hating macOS or anything, and as I said, using both for a very long time.

The apps I have given as examples are KDE's default apps and maintained by KDE project themselves. They are part of the default installation.

Homebrew/nix: The most obvious one. MacOS just has no good package manager. It's even worse than Windows, which is also pretty bad, but at least on Windows you can install an app and manage it in a central "Add and Remove Programs" view, and they've standardized an installer format that cares about and manages versions and upgrades.

Middle Click: This is a galling one.

Rectangle: Far better than the MacOS's native snapping, which is half-assed.

AltTab: MacOS's keyboard driven app and window switching are terrible. It feels like they don't test for use that's not entirely mouse-based.

Mac Mouse Fix/LinearMouse: Real mouse support on MacOS sucks, and the unified settings between mouse and trackpad really sucks when you have to occasionally use both and don't want them to behave identically.

Karabiner: MacOS's keyboard mapping is incredibly underpowered.

AeroSpace/yabai: I don't use these anymore, because these also were pretty buggy for my use case; instead, I just use MacOS without Spaces. I hate MacOS window management, but find it less painful if I just lean heavily on tmux. MacOS Spaces are completely broken, especially on multi-monitor. They never do what you expect. I could write a screed on exactly how broken they are, but I won't in this post.

Ice (might be sketchy now; had an ownership change): Lack of menu bar overflow on MacOS is awful. I have icons that just disappear into the notch and can not be clicked, and there's not space for much, especially if you use something like Stats to see resource use.

BetterDisplay+MonitorControl: Non-retina monitor management on MacOS is bad.

SoundSource: Per-app audio control just doesn't exist otherwise.

These are all things that work fine out of the box on KDE and even Gnome. MacOS, for a very UI-focused OS, is simply terrible to use graphically if you're not baby-ducked into it from a young age. I've been using it for years at work (because my options are MacOS and Windows, and MacOS for all its flaws is still less painful than Windows), and I still can't get used to all the bad decisions. Spaces are the most shocking example of something that should work that doesn't, and they still don't fix it year after year.