Chakra, like money, is a means to an end. If having large amounts of chakra is a genetic occurrence in the Namikaze clan, then it's because the actual kekkei genkei jutsu (if it exists) requires it.
While I know nothing about it, I would've expected Jiraiya to teach him this clan jutsu if he could, and if Naruto was able to learn/activate it.
This leads us back to Naruto's comment of " Now I can do it..." to Pa frog, which he immediately stopped talking about. Did he just mean, wind release shuriken rasengan, or "that jutsu", or this other jutsu (the kekkei genkei)? (Another thread/s on this btw).
Recall there are clans like the Aburame (bugs), Kiba's (dogs), Shikamaru (shadow/darkness), but that are not kekkei genkei's. Naruto asked about this, when learning to manipulate elemental chakra, which leads me to think it's not that either since Jiraiya might've mentioned it.
Maybe it is just large amounts of chakra, not a kekkei genkei, and FTG jutsu is forbidden like Kage Bunshin because it requires too much chakra, or the speeds are too much for a normal person to endure. Just remain open that it could be either kekkei genkei, clan-specific, or forbidden outside the 4th Hokage and his legacy. I am open to being wrong.
Finally, it may be there, but plot-wise, it's hard for him to activate a kekkei-genkei or clan-specific jutsu and not figure out his past. That's what would hold it back in the story.