I read the manga weekly for ~10 years.
The second part falls apart pretty bad imo. It's not horrible at least completely but you could definitely say there's a bait and switch from the first part of the manga, prior the time skip.
Shit is supposed to be about ninjas and the art of being a ninja but like >>68945 said it just devolved into ebin power level shit.
They also never explain some of the more intricate stuff regarding chakra, like how non elemental shit works like Shikamaru's techniques, although they tease that they'll explain it later. The real god techniques of the series are seals, but they never explain those either. The last three years of the manga I'd say I definitely read it just begrudgingly.
Not to mention, I mean, Itachi probably could have solo'd Pain and/or Tobi and lit the Gedo Mazo on fire at stopped the whole thing from ever progressing but didn't so he could let Sasuke kill him and set him on the right track but none of that shit worked out the way he wanted to anyway…