Some people like subtle and understated menace. Just as some don't prefer Vader slicing and dicing his way through Rebel fleet troopers in Rogue One -- it's just a stylistic preference.
The Vader vs Rebels scene in RO was a dream come true. Its been IMO the best thing Disney's put out thus far with their SW franchise. They really should just make a Vader movie already, before James Earl Jones passes. Have it take place between ANH & ESB or between ESB & ROTJ. They recast Solo & Lando so they can recast Luke and Leia too. Vader is the Chosen One, that means his skills with a lightsaber should be as brutal and grandiose as they were in that scene.
As for Palpatine's speed in Revenge of the Sith, like the Chosen One, he's basically the ultimate Sith Lord (now we know after watching Rise of Skywalker). So the guy should be pretty insane with a lightsaber too. Never understood people that were surprised he was a powerful swordsman. Why wouldn't he be? He's the guy who trained Maul who was an awesome swordsman. I love how quickly he killed the three Jedi Masters who came with Windu and how he kept Windu busy until he sensed Anakin arrive and threw away his lightsaber to fake vulnerability. I also love how Yoda actually gave him a good fight and both their lightsabers were lost in the duel.