Grievous, for me, just ruins the depiction of Vader in the OT. If Grievous has such advanced cybernetics, why is Vader a lumbering bodybuilder who can barely raise his arms over his head?

The canon can do the “Palpatine evil” explanation all it wants, it still doesn’t make sense to me.

PS. If you have four lightsabers and are fighting Obi-Wan Kenobi - who has only one lightsaber - just attack with all of your lightsabers - from multiple different directions - at once in ways that he can’t parry every single attack.