Far from it. Count Dooku, aka Darth Tyranus, was one of the most powerful Sith Lords, not just during his time, but ever. Dooku practiced Form II of light saber combat, Makashi, which focused heavily on technique. He was not only a master of it, but most likely the greatest practitioner of the form ever.
Despite all that, Dooku was an extremely powerful Sith, both in the Force and with a lightsaber. He defeated both Obi-Wan Kenobi and Anakin Skywalker in combat and went toe to toe with Yoda, holding his own with the Jedi Master.
Count Dooku was a menacing Sith Lord and central figure in the Clone Wars. Once a Jedi -- trained by Yoda -- he became disillusioned with the Jedi Order and thirsted for greater power.
It's not even up for debate that Darth Vader is stronger than Count Dooku. Even before he was at full power, Anakin Skywalker was able to overpower Dooku simply based on his lightsaber training. Had Dooku fought Darth Vader at full power, the fight likely would have been a lot shorter.
When Dooku was still with the Jedi Order, he was considered to be one of the greatest (if not the greatest) lightsaber duelists of his generation. Anakin really wasn't as good of a duelist as many people hype him up to be.
Indeed, Palpatine seems to have seen Maul as an ideal apprentice, admitting he was "a loss" compared to Dooku in Darth Vader #20.
That notwithstanding, Master Windu was also one of the best. If the two spared as Jedi, Dooku would probably win the match because he was the better all-around duelist.
While serving Darth Sidious, Dooku is a ruthless terrorist and warlord, whose methods included torture, murder, and even genocide. However, before turning to the dark side, he was a respected Jedi Master, having been trained by Yoda and served as the Master of Qui-Gon Jinn.
1. Darth Sidious (Star Wars: Episode I – The Phantom Menace) Truly, the most powerful Sith Lord was Darth Sidious, better known in his public persona of Chancellor (later Emperor) Palpatine. Through cunning and manipulation, Sidious killed his master to claim the mantle of Dark Lord of the Sith.
By far one of the cruelest Sith to ever live, Vitiate was created as an antagonist for the game Star Wars: The Old Republic, in which he was responsible for killing his parents at age ten, and later kickstarting the Mandalore Wars, the Jedi Civil War, and in his quest to remain Emperor of the Sith for all time, the ...
According to Star Wars Legends content, the first Sith was a former Jedi Master, Ajunta Pall, who became a so-called Dark Jedi, or “Fallen” Jedi. As the name implies, these Force-sensitives chose to practice the Dark Side, and rejected the Light Side of the Force.
Emperor Vitiate was a Sith Lord who successfully gained near immortality by draining the life force of an entire planet, later attempting to drain all life in the galaxy, which would give him true immortality.
During that battle, he learned why Qui-Gon supported and defended Anakin, when he showed how strong his connection to the Force is. Dooku had very little respect for the young Jedi Knight, despite his bravery and unbelievably strong connection to the Force.
Despite Grievous hating Dooku, he continued to serve him and even saved his life during Invasion of Dathomir.
Dooku was powerful and extremely skillful with his lightsaber, to the point he easily beat Anakin and Obi-Wan. Still, Dooku was less powerful than both of his masters – Darth Sidious and Yoda.
In Star Wars Legends and Canon, Galen Marek (Starkiller) is the only Jedi (other than Obi-Wan Kenobi) to put a beat down on Darth Vader/Anakin Skywalker. Galen was secretly trained as a Sith Lord apprentice to Vader, but returned to the light side and the Jedi.
There is no doubting the fact that Count Dooku was a great duelist and was an even more fearsome Sith Lord because of his strength in the Force. But Darth Vader was chosen as his replacement for a good reason, as he was simply stronger than him.
Yoda had to shoulder that decision for years. However, he ultimately understood the importance of life, and the power he could have used to defeat Dooku would have been much better used to preserve two lives. Over the years, Dooku would commit countless atrocities and also suffer incredibly embarrassing defeats.
Who wins between Kylo Ren and Dooku in Star Wars, and why? Easily dooku, 9 out of 10 times. Darth tyrannus is a former jedi, who is more than able to fight fully trained jedi and their skilled padawan at the same time. Kylo Ren is at best on par with that skilled padawan.
Yoda will most likely win in a fight against Darth Vader because he is more skilled with a lightsaber and has the experience and feats that allow him to trim whatever size and strength advantage Darth Vader has over him. In fact, Yoda nearly defeated Palpatine, something that Vader could never do.