There are plenty of idea for Boruto to get stronger without the need of lame concept like jougan.
We have Byakugan that if we trace the origin the eye it can dimensional travel and killing people just by staring at them.
We have Uzumaki blood inside Boruto. Where brilliant writer can use it, exploit it and expand the power of uzumaki. An unexplored territory. Give Boruto super powerful chakra chain jutsus which he needs to discover, unlock and learn. Make Boruto travelled to unknown place or territory where in there he found long lost treasure that's Uzumaki sacred scroll that contains thousand of jutsus.
To shape him to be very strong shinobi in the future like his Senju/Uzumaki predecessors.
For starter give Boruto large chakra reserve because he's related to Uzumaki-Senju-Hyuuga-Otsutsuki. Then give him Byakugan. I remember one of Kishimoto next generation conceptual illustration have Boruto with Byakugan eyes. The concept is very neat. And the next step develop his Byakugan power to reach Otsutsuki level bcuz Boruto is so special. Then focus on developing his Uzumaki specialty especially in fuinjutsu.
Talking about NV threat rn they aren't that stronger than Prime Kaguya unless they consumed CF. There is nothing suggest that Isshiki is planetary or dimension level
So I think the skillsets is enough for Boruto.
It has never really been confirmed that the byakugan itself is responsible for interdimensional travel. As far as we know, that is just something that a bunch of Otsutsuki can do.
Kaguya used her rinne sharingan for it.
Urashiki and Sasuke use the rinnegan for it.
Jigen just uses the karma (no dojutsu at all)
Obito used the mangekyou sharingan to connect to Kaguya's dimensions
Momoshiki had both the rinnegan and the byakugan, but we never really saw him use whatever space-time technique that he used to traverse dimensions.
We saw Kinshiki in the anime use a kamui-like space-time jutsu, but we don't really know if that stemmed from his byakugan.
As for the whole killing people by staring at them thing, that was some weird unexplained filler. I could accept it, but that really should have been expounded on more.
Also, about your statement about the current threats not being stronger than Kaguya unless they ate chakara fruits:
The Otsutsuki have been established to have been eating chakara fruits for generations. Momoshiki alone has been seen eating several of them. It is likely that Isshiki has eaten his fair share as well.
Even if they did go the "normal shinobi" route (with Boruto not having anything special like the jougan), knowing this fanbase, you guys would still probably call asspull bad writing if Boruto became any stronger than Iruka.
Plus, Boruto doesn't have time for all these years of training. This isn't DB where they get warned about threats two or 3 years in advance like in the Saiyan saga or the android saga. In the NV, threats just come when they come.
I for one like the jougan. Maybe you can blame Kishi on this, but I kind of almost don't even have faith in the abilities of "normal" shinobi to be really powerful since back in Naruto you basically had to either be a jinchuuriki (of Kurama or the juubi), an Uchiha or Hashirama to reach top tier. Just look at Konoha 11. They weren't even allowed by Kishi to learn elemental techniques or anything other than their clan techniques.
