Just because a slight delay doesn’t bother you it doesn’t mean it isn’t there. The first times I used GNOME I actually was convinced it was some issue with my computer / setup. After countless installations on different distros and also dealing with it at work and friend’s computers I came to the conclusion that is it slower than Xfce and most likely KDE. There’s no way around it.
To be fair, as you said in another comment I don’t believe this is CPU bound at all, nor GPU. Multiple machines some Intel with iGPUs others with discrete GPUs, others with AMD, all the same behavior. I’m way more inclined to believe this is an I/O issue above all, GNOME needs to read and load a lot more stuff than Xfce to render any window thus it will be slower.
Anyways, I never experienced this much, but if you google around people that are using older machines say that GNOME is always the slowest thing on those machines. Others such as Xfce they report it as performing better, so if on an old machine the slowdown once using GNOME is noticeable by almost everyone it means it does indeed use more resources. You can throw an i9 to at the issue but the fact is that it will always use more resources no matter of the hardware you have.
In my case I tend to be particular sensible to small delays than you or others but it’s there and old machines prove it. It’s not that I can’t use Gnome ever or it provides the worst desktop experience ever, no, it works fine and can be productive but I notice the delays.