That's right. In the manga and anime, Goku said he can't access it anymore.
There were differences in how he accessed it, as the anime only kicked in after he was beaten down or near death, while the manga simply randomly activated mid fight with Jiren, without requiring massive amounts of punishment.
Being unable to access it post ToP at will is the same in both mediums.
__________________ What CDTM believes;
Never let anyone else define you. Don't be a jerk just to be a jerk, but if you are expressing your true inner feelings and beliefs, or at least trying to express that inner child, and everyone gets pissed off about it, never NEVER apologize for it. Let them think what they want, let them define you in their narrow little minds while they suppress every last piece of them just to keep a friend that never liked them for themselves in the first place.
This was a limit only imposed by the creator though. Goku has never had trouble reaching a state he’s acheived before. It’s saijen biology that can keep achieving greater levels based on their past.
I really feel that Goku is nessecary could hit UI if the time called for it.
They also usually show the last form can't beat the new villain. The fact Toriyama did away with it, implies a truely mastered MUI might be beyond even a Broly or Vegeto.
__________________ What CDTM believes;
Never let anyone else define you. Don't be a jerk just to be a jerk, but if you are expressing your true inner feelings and beliefs, or at least trying to express that inner child, and everyone gets pissed off about it, never NEVER apologize for it. Let them think what they want, let them define you in their narrow little minds while they suppress every last piece of them just to keep a friend that never liked them for themselves in the first place.