This is the reason a #Shimano XT #derailleur costs more than a Shimano Alivio. On the left you have the whole-body slop of an Alivio M3100 derailleur. On the right you have the same of an XT M8000. There's noticeable slack in all the pivot joints of the M3100. There's no noticeable slack in the XT. It feels like a single piece. The result of this difference is misshifts like going one gear higher then back to the desired one, or otherwise some shifts taking longer between gears.

There's a second video in the original post showing the XT derailleur.