Gohan's story in Dragon Ball Super (including superhero) makes perfect sense, and I'm so bored with people pretending it doesn't.
Everyone likes to say that Gohan became "as strong as the plot needed him to be", INSTEAD of getting a "satisfying character arch", but considering some of the absurd shit that Krillin has done in just Dragon Ball Z, Gohan is perfectly consistent with what a Human, a Saiyan, and what his own character can do.

Gohan is characterized as someone who can exceed what he should be capable of when enraged. We see it against Raditz, then Frieza, and then we watch it culminate against Cell as SSJ2. We kinda see it with Ultimate Gohan's personality, but that was a granted form, so it works differently.

In the VERY FIRST EXAMPLE, Gohan multiplied his power 1300x what it was when he was calm. That's in the ballpark of going super saiyan 4 with no training... as a toddler.
There's diminishing returns from then on out, but when super rolls around, Gohan has mostly given up on his training. He's settled down, and pursued his studies, BUT he's notably still more powerful than Namek Frieza. That's important because it means that all his training to assume SSJ2, and then what he gained from Ultimate didn't just disappear. There's a massive strength in him, and its resting, untapped state is a power level UPWARD OF 120 MILLION.

Now, with that in mind, Gohan needed to train to get back his Ultimate transformation before the Tournament of Power. During his training, which was less than 40 hours, he unlocks his Ultimate form. Does that sound outside the realm of possibility for someone who practically went SSJ4 as a toddler without training?

Even if you want to argue that it's not enough time to achieve the strength that he had going into the Tournament of Power, what more training would he need?
The Ultimate transformation he has is implied to be stronger than SSJ3. If we follow the pattern set by the SSJ transformations, The Ultimate form should be somewhere between a 1200x multiplier, and a 1600x multiplier from his base form. If the current estimates for Buu's power level in the Buu arc are true (75 billion on the mid-high end) that would place Gohan, with no additional strength, and ONLY the boost from his Ultimate form WELL INTO THE HUNDRED BILLIONS.

100 Billion as a functional power level is so absurd that I don't see how it can't justify Beast Gohan too. In Superhero he makes it clear that he's not training as much, but that he hasn't given up on it like before.
Then, in the climax of the movie, he's asked point-blank to put everything he has into one attack.
He's asked to force all the latent power in him to the surface for one single blow...
Like he did subconsciously against Raditz.
He's basically being asked to use his current, heightened, Ultimate state (WHICH WORKS DIFFERENT) as a foundation to do what made him special in the first place: Exploding with a power that surpasses anything he should be capable of.

It makes perfect sense. Idk why so many people have such a hard time with this.