Why didn't Naruto uses his full power that he demonstrated in `Boruto chapter 52` against Sasuke or `Kaguya Ōtsutsuki`

Question

In Boruto chapter 52 Naruto demonstrated unsual high power which made him so much powerful that he almost solely defeated Isshiki Ōtsutsuki.

So if Kurama had this power than why didn't he give that power to Naruto in his fight against Kaguya.

Naruto power is described as

Sasuke : Such tremendous chakra. He never told me he had move like this. What is it.

Kurama : Think of it like nuclear fusion. It's similar principle to how the sun produces energy.

Naruto : Nuclear fusion? What's that?

Kurama : never mind. the theory doesn't matter. My chakra and your chakra are serving as the kernels to produce a whole other new type of energy. That's all.

Answer 1

Because of the terrible after effects. Against Kaguya, they had better alternatives. And Naruto had many other cards up his sleeve too.

Answer 2

In the series, because they didn't want to just sacrifice. Though it´s "suspicious" Kurama didn´t even mention the ability those years back, considering how powerful was Kaguya.

In a meta sense, that's just because it is an invented power-up, which was just recently retconned into existing. So Naruto didn't use it and Kurama didn't mention it against Kaguya, because Kishimoto hadn't even thought about it yet. Also, stop for a moment and think: how someone like Kurama even knows what nuclear fusion is? We know Naruto is an idiot and doesn't know, but he is also the hokage, so how a chakra beast knows the term while he doesn't? It´s kurama reading science books in his free time or what...?

Answer 3

If he used Baryon Mode, the fandom would go crazy, well at least some people.

If Naruto used Baryon Mode against Otsutsuki Kaguya, he would gain the strength to defeat/kill her all by himself, and the crew would probably make him do so. Then Boruto's karma would be introduced and the Naruto Fandom would be like "Why didn't Naruto get a Karma seal after killing Kaguya with Baryon Mode?!?!"

Secondly, Baryon Mode is the price of Kurama's life. There'd be no need for its use when together, Obito, Kakashi, Naruto, Sasuke, and Sakura were enough to stop Kaguya and Black Zetsu. It would be a pointless sacrifice when Naruto already had the power to stop her without it.

Third, Naruto and Sasuke were written off to be equal in skill. If Naruto used Baryon Mode, his skill would be far ahead of Sasuke's, then Kurama would die, then that would make Sasuke stronger. If Naruto used Baryon Mode it would mess up the way the series wrote Naruto and Sasuke to be equals.

Fourth, the Boruto staff hadn't even thought of Baryon Mode. It was mostly created because the strength of Naruto and Sasuke wasn't enough to stop Isshiki.