I strongly don’t recommend Naruto Kai and I feel like it partially ruined my experience of the anime.
All due respect to the creators for their work on the project, but while the idea sounds great in theory, I don’t think it plays out well.
When the manga was still coming out, I caught up to when chapter 500 was still new. I had already seen part 1 of the anime (sans the massive filler), waited forever for Shippuden to catch up, watched Disney XD, then years later sought after a way to finish the series but was immediately overwhelmed at the notion of filler that I assumed would be of similar quality to part 1 (which to be fair I only watched a few episodes of, and enjoyed much more upon revisiting them).
After I found the supposed solution to this and binged Naruto Kai, I really felt like I had missed out on certain filler arcs that contributed to the world building, gave side characters more screen time, or gave backstory to main characters and important events that were glossed over or ignored in the manga.
Years later, after the dub had been completed I decided to watch Shippuden again, starting at season 2 (right after team 7 gets back from Orochimaru’s hideout). Having just finished season 2 (including the filler arcs) and just reaching the Taka arc, I realized something.
My main problem with Naruto Kai wasn’t necessarily because the filler mostly wasn’t as bad as the internet made it out to be, but rather that it absolutely disregarded any sense of pacing and just rushed through everything without letting things breathe. The pacing of Naruto is already pretty bad, but Naruto Kai’s was equally bad (if not worse) but for the opposite reasons.
I feel like some of the padding and anime-only scenes actually served to enhance the mood of certain scenes and gave the viewer a chance to chill, they were sometimes a part of setting up set pieces or establishing certain settings in more detail.
Something that using the manga as an editing guide neglects is that reading manga allows you to stop and take things in at your own pace, whereas just flipping through it frantically like Kai presents it just makes it feel hyper caffeinated. Sometimes it’s okay and even beneficial for things that don’t have plot importance to happen. Even books have a bunch of random details that don’t really support the plot, but it helps to center the reader and put them in its world in a way that feels authentic and not just like cliff notes.
Tl;dr: Kai rushes through things and it kills the moods that the anime’s directors try to create, among other things.