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In fact, I'd go as far as saying that the animations not being smooth should be considered a bug. That'd mean synchronous I/O in mutter, or a horrible block I/O scheduler in the Linux kernel.
I've never seen smooth gnome-shell overview animations on my Intel Clarkdale (2 Cores, 4 Threads, 3.2GHz Frequency, 733MHz GPU Frequency) system from 2010. Same on different other machines, all newer (and better iGPU). Seems like you are pretty lucky.
Especially the fade in transition on user login has never been smooth either: https://bugzilla.gnome.org/show_bug.cgi?id=747599
Anyway, animations should be disabled on virtual machines, but they are not: https://bugzilla.gnome.org/show_bug.cgi?id=771311
Regression caused by this? https://bugzilla.gnome.org/show_bug.cgi?id=745104
I was told that the virgl support would be built into Fedora to go along with the GNOME releases. That was added in GNOME 3.20.
Maybe animations should even be disabled on all machines older than (e.g.) 5 years by default.
I've seen smooth animations on 8/10-year old machines, though an SSD upgrade will help the effects of the sub-par scheduler for interactive uses.