Jiren is now the most powerful mortal in the whole multiverse. Even the Gods of Destruction who witnessed his power were very surprised by what they saw. And not only that, he appears to be something more than a God of Destruction. He might’ve been achieved something that only some have achieved.
Ultra Instinct is the state that was introduced in the latest episode of Dragon Ball Super. This is a state where a person doesn’t have to think twice or even once before attacking or blocking. A person who has achieved this form does not only attain strength on his fighting style, but it also enhances defense by accurate blocking and dodging.
Goku attained that in the Tournament of Power out of desperation for his life. He absorbed the Spirit Bomb and was able to reach that state that even the Gods cannot get easily. Though I am not really surprised by Goku’s extraordinary feats. Why? I have seen it already, and not even just through Whis.
That’s right, Jiren seem to have that power already, the Ultra Instinct. His movements are similar to Goku’s movements. While Goku is the exception to the rule, Jiren and Whis has attained it and mastered the art of accessing it at will. While Goku got his version in the sudden burst of power from the Spirit Bomb, Whis and Jiren got a colossal amount of Ki already that they didn’t need to transform just to attain Ultra Instinct.
Here’s a catch on Jiren’s side: while Whis is an Angel, Jiren is still a mortal. Jiren needs to save his energy as being in that state drains the user’s Ki which is needed to attain that state. Or it can be the other way around, Jiren needs to control his colossal ki so that his ki will not damage his body. And to do that, he needs superb Ki control training which can be done through meditating. We have seen him meditate a lot before the Tournament.
Goku’s Ultra Instinct form (I still prefer to call it the Limit Breaker form) was short-lived because his gas ran out. His body is not trained to use that so much Ki, but because of his control, the Ki leaked outside his body instead of bursting out.
I think the reason why Goku cannot keep up with Jiren before was that of Jiren’s ultra instinct. I mean, hey, Goku’s Super Saiyan Blue Kaioken x 20 should be faster than Hit’s time skip. It just means that Jiren is really a master of reflexes because of his Ultra Instinct. Jiren doesn’t even need to predict Hit’s movement in the next fight just like Goku did the last time. Jiren’s own body has a mind of their own and will move accordingly when they sensed danger.