The greatest strength of Naruto is its characters's stories. As a series with such a long runtime, Naruto has the chance to introduce and flesh out numerous characters, and because it is so long, I ended being quite attached to them. One of the strengths of this author is creating strong emotional backstories for his characters, and this was by far the best aspect of Shippuuden for me. The never-give-up attitude of Naruto is a staple of the shonen protagonist, but I feel Naruto owns and embodies this quality so well in a world filled with people who have given up in one way or another that it becomes his own.
The infamous talk-no jutsu, the tendency of fights in Naruto to include an actual argument between Naruto and his opponent, is in my eyes one of the strengths of the series, because it made all those conflicts more than power struggles; they were also ideological conflicts. I am not claiming that the ideological struggles in question were deep necessarily but it does give them more meaning.
One thing that impressed me with Naruto in general and is reflected in Shippuuden is that even though the story went on for so long and in some ways it's clear more than one retcon happened over its run, the world it constructed was remarkably well-rounded and all the dots were connected. For me this was never more clear than during the double episode revealing the circumstances of Naruto's birth, which managed to explain everything we knew from the first series and link to everything we learned afterwards, even though I'm willing to bet it wasn't how Kishimoto had imagined it would have gone when he began this story.
There are some big weaknesses to Shipuuden.
The most obvious one is the incredible amount of filler. While some arcs could be worth watching, overall they should be skipped. Some of them are so nonsensical that they can be fun to watch as basically a self-made parody of the show.
A sore spot that stands out for me is its female characters. I wouldn't say Sakura is as useless as the meme says, but it highlights how overall, the author has a really hard time giving them a story where they have agency, even if said female character is part of the main cast. There are still a few gems, mostly Tsunade.
Also the third arc is the weakest of them, despite having many epic moments and great characters, the way they are all bundled is pretty weak story-wise (notably a certain problem about masterminds in the shadows on repeat).
Nonetheless, when all is taken into account, this series is undoubtedly one of my all-time favorites. Its worldbuilding, fights and characters are just so memorable. It's not the best anime by any measure, superior entries exist in almost all regards. But Naruto has a way to make you care about its characters and get invested in their story that excuses all the filler in the world.
