IMHO, the problem isn’t that it’s on by default, it’s the fine tuning of the feature. The velocity and pattern needed to trigger it + the lack of a reasonable max scale.
MacOS has had this on by default for a decade, but it feels more intentional when it appears. Meanwhile, I litterally still see KDE threads from people trying to troubleshoot “bugs” about their cursor size.
The KDE cursor needs about 15 min of a motion designer sitting next to the engineer that coded this.
I legit thought it was making the cursor "closer" because windows were layered on top of each other and it was doing weird depth scaling or something LOL.
I was going to suggest setting a delay in Spectacle, but seems like the enlarged mouse cursor does not show up in screenshots, even if you set "Include mouse pointer"...
Plasma's shake cursor plugin is a pretty recent addition, according to KDE's GitLab it originally got merged just 10 months ago. Enabled by default since 6.1 (June 2024), with high-resolution cursor coming shortly after that iirc. So it's basically the same as on macOS now, but only since a few months. I don't know exactly when macOS introduced it, I've read somewhere it was with El Capitan, so that would be 9 years ago. Either way, macOS definitely had it first.
They added this thing to find your mouse, by moving it the cursor gets bigger and bigger
Shake Cursor makes the cursor grow when you "shake" it. This helps you locate that tiny little arrow on your large, cluttered screens when you lose it among all those windows.