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 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.