To each their own. I agree with your statement but have to disagree with some of your points.
Not all OG characters are nerfed, Sakura in particular is one of the strongest ninjas in the series. The nerf has to happen to:
1. make way for the new characters. If the predecessors take most of the spotlight, the series might as well be called Naruto: Naruto Next Generations.
2. Stronger characters are introduced - the Otsutsukis, the progenitors of Chakra, supernatural stuff etc. Naruto and Sasuke weren't nerfed, they were just outmatched.
3. The loss of Kurama was necessary. If Kurama didn't die, there would have been no stakes.
Boruto is the successor of the Naruto manga. Originally, it was a series succeeded by Naruto but with a different staff comprised of Ukyo Kodachi (the author), and Mikio Ikemoto (the illustrator). Masashi Kishimoto has since replaced Kodachi and needed to adapt to his writing and come up with ideas for the manga. Vinland Saga on the other hand is an ongoing manga since 2005 with its original author, Yukimura supervising his own series. Yukimura also has 4 assistants helping with his manga.
Boruto's art isn't bad, every illustrator has their own style. Vinland Saga's art style is really clean though.
TLDR; It's unfair to compare a newer series to an older one where Boruto hasn't even reached its halfway mark compared to Vinland Saga, a series that is reaching its end. Me calling the Boruto manga goated sounded far-fetched, maybe I should have phrased it better.