Naruto wasn't bad or too bad until the last arc though.
Pain Invasion saved it, and had Kishimoto kept that momentum, it'd have been great. Bleach, I dunno. One Piece is debatable as many say the first few arcs weren't that good, and many say the arcs after the timeskip are bad or whatnot.
FT though is kind of unique? I mean, it was shit from GMG 'til Tartaros (dunno how many arcs passed between those two), and then it went back to shit. Or was Bleach like that too?
The last arc of Naruto you talking about is the 4th Shinobi War? It's 1/3 of the manga, and honestly it was
that bad.
Maybe Naruto at its worst never got as bad as Fairy Tail's worst... but they aren't that far apart. It's the same bullshit: dead characters are brought back to life, villains are super hyper but are defeated by ridiculous means, etc.
I agree about One Piece being not so great before the Grand Line, but the author was preparing it for something bigger. I think overall One Piece maintained some great consistency then, even if on average it's not as good as before after the time-skip. Dressrosa in particular dragged on for literally over 1 year at some boring parts.
About Bleach... it wasn't anything amazing before the Seireitei arc. The consensus is that Seireitei arc was the high point of the series. I also think the Hueco Mundo arc was still great, while some do not see it that way.
But the Fake Karakura Town arc was shit. The Espadas were disappointing. And Aizen was a boring villain. He won't shut up and humiliates everyone, yeah yeah I got it.
After that we got the principle of an amazing arc, that was the Quincy invading Seireitei. Have you read it? The first part was amazing, but... after they reach the Royal Palace, it becomes one of the worst things I have ever read.
There are too many characters, and none of them do anything important. There are too many plot points, and none of them are resolved. And the big bad is super annoying, and possess a series of reduntant abilities that makes him win any fight instantly. And the final battle ends abruptly, and the big bad looses pathetically.