You prompted me to try out the little-known web version of Keynote on iCloud.com. I expected it to be surprisingly good if not quite up to the desktop standard, since Apple's front end web teams do amazing work. And sure enough, that's what it is.
I focused on animation features and it has most of those available in the desktop version, but it's missing a few (e.g. action build effects). It's also missing some of the image adjustments. But it's got Magic Move, and shape subtraction/intersection[1]. Most importantly feels pretty good to use, though it takes a while to load (on Chromium). I've no idea if they implemented that inner-detail object alignment - don't have an easy way of testing it.
[1] https://support.apple.com/guide/keynote/combine-or-break-apa... - note the feature about breaking apart SVG images too, I wonder if that's related to the inner-detail trick.
