Even Ultra Instinct wasn't pushing Jiren a lot. Like, I'd say they were not equals in term power, but Goku is a fighter who adapts as he fights. If Goku is able to overcome Jiren, I can't see it being without that. Or maybe, just maybe, here me out here. The time limit ends and it's a 3 way draw between Goku, Hit and Jiren. (Universes)
Been reading up on some theories and I guess that this isn't the last time we'll be seeing ultra instinct. Frieza will give Goku some energy, Hit and Vegeta will buy him some time and maybe Goku will go full Ultra- whatever and box Jiren. Only like 25 minutes left in the tournament so I guess it'll happen within the next five or so episodes.