It's a pretty simple answer but no, it does not. A guidebook for
We all know that Super Buu is about 8X stronger than SSJ3 Goku. Not only does this show that GT Goku is stronger (He fought people STRONGER than Super Buu in base form.)
GT Goku is so broken that he blows Super out of the water at the end of GT, even in his base form he's still one shotting a lot of the heavy hitters of late super. And even though he can't defeat people like Broly, Jiren, and Beerus in base, he can just transform.
So he is about 400 times stronger than Z's Goku, and about 40 times stronger than Super's Goku at base. And a super saiyan 4 GT Goku is about 400 times stronger than a super saiyan 3 Super Goku.
In the anime-only sequel series Dragon Ball GT, Goku is transformed back into a child by an accidental wish made by his old enemy Pilaf using the Black Star Dragon Balls while Pilaf was about to wish to take over the world.
Dragon Ball GT opens five years later, shifting Goku to physically 42 but chronologically 49 years old. Emperor Pilaf steps in to complicate things even further after reverting him back to an 11-year-old while retaining his adult mentality.
While they should be seen as a continuation of Goku's story, it is not necessary to watch either Dragon Ball Super or Dragon Ball GT. There are some great moments in these shows but they aren't required viewing for Dragon Ball fans.
This is a phenomenal display of strength, but Goku learns that his temperamental new transformation still isn't enough to beat Jiren on his own.
Canon material is everything based on a continuity that is officially confirmed by the owners, so in that respect, Dragon Ball GT is, technically, canon, even if the events of the Super disturb the logic from time to time.
Multiply that by 100 and Timeskip Base GT Goku would be 6400x stronger than Omega Shenron. With that amount of strength his power would be more comparable to MUI Moro arc Goku while only using SSJ.
It's a pretty simple answer but no, it does not. A guidebook for Dragon Ball GT called the GT Perfect Files states that he did not get any weaker. However, he does have a harder time maintaining his super saiyan transformations.
While the latest power-up Goku has reached in Dragon Ball canon is Ultra Instinct, one episode of Dragon Ball GT reveals that he seemingly unlocked that ability long before Dragon Ball Super was ever conceived–and he did so when he became Super Saiyan 4.
Immortality: As shown in Dragon Ball GT: Hero's Legacy, Goku cannot age and will presumably live forever. It is unknown if this immortality extends to him never being killed, but he certainly has eternal youth.
With the snap of a finger, Zeno is capable of erasing entire universes from existence, so regardless of Goku's Saiyan abilities, his mortal constraints will almost certainly prevent him from overpowering Zeno.
Specifically by the original creator of Dragon Ball, Akira Toriyama who walked away from the project insisting he didn't want to work on Dragon Ball anymore. This resulted in the series essentially being filler as it had no previous source material and was just a studio made product.
Aside from designing a few characters, Akira Toriyama was largely uninvolved in Dragon Ball GT's development, and it shows. It takes place 15 years after the end of the Majin Buu Saga, and 5 years after the end of Dragon Ball Z.
Despite the fact that it is also the most controversial Dragon Ball series and that SS4 is not even canon anymore, the power-up was so different and had such an amazing design that fans keep loving it. Super Saiyan 4 still shows up in the games, fan-fiction, and non-canon stories.
1) Beerus. Although Jiren is said to be able to defeat a God of Destruction, it's unlikely Beerus is at risk of suffering that defeat. Beerus has yet to use 100% of his powers in Dragon Ball Super thus far, whereas Jiren at 100% struggled against Mastered Ultra Instinct (MUI) Goku.
Jiren was able to survive an assault from Mastered Ultra Instinct Goku, putting him on a truly elite status within Dragon Ball Super and DB in general. There's no question that with this level of strength, Jiren could resist diluted Hakai energy.
They decided to not have Goku return to normal because they would have to collect the Dragon Balls all over again as Goku decides he would rather stay looking like an 8-year-old until he is an adult again than have to travel the galaxy again for the Dragon Balls, so they leave, but Dende gets an evil look and starts to ...
Toriyama did, however, come up with the Dragon Ball GT name, which stands for "Grand Tour", in reference to the series having the characters travel through the universe, and designed the appearances of the main cast. Toriyama himself referred to GT as a "side story of the original Dragon Ball".
The show was created by Toei because Toriyama was done writing Dragon Ball at the time, but they wanted it to continue, because it was their biggest moneymaker, so they created GT instead of waiting for Toriyama to write more, which is basically what filler is.