> That's up to personal preference.

Stated preference perhaps, but unlikely revealed preference.

Depends on context, but for a computer on which you're doing work, moving wallpaper is usually a net negative for usability while you're actively working, though the magnitude depends heavily on the animation.

The problem is primarily peripheral attention. Motions is a strong pre-attentive visual signal: your visual system detects it without you deliberately deciding to look at it. One a laptop where you're close to the display and spending long periods concentrating on text, code, documents, etc., any visible animated region around or through windows can create low-level competition for attention.

A good compromise is wallpaper motion during transitions or stillness during work.

Broader UI principle: motion should explain change, not create change to be noticed.