Why is Naruto not as good as it used to be? Hrm, I wonder. I'm going to give this a much longer and more thoughtful response than should probably bother with.
Once upon a time, in the first half of the series, Naruto suceeded on many levels.
1. Sure it had the gatuitous training arcs, but it was paced well and those were rewarding, Naruto finally pulling off the Rasengan after practicing it so long at a desperate moment was satisfying.
2. It balanced about two dozen characters, giving them all unique abilities, regular screen time, and different personalities.
3. There was a little romance, a little fighting, a little intrigue, a little fanservice, and generally, any given chapter would unveil a little bit more about the world and the characters. A good balance.
4. The fights were well done. Even the 5-10 chapter fight scenes tendd to have a fair ammount of variety and surprises, and there was actual planning involved. A fight might have a setup done at the start of it (Naruto makes a hole in the ground in a much earlier fight, which Shikimaru then capitilizes on, for instance). To this day, the Rock Lee/Gaara fight is still incredibly epic to go through. The balance and back and forth there was amazing.
5. The series was almost all consistently very well drawn.
6. There was a certain ammount of intrigue, and it seemed like there was a greater plan and story in motion. Orochimaru was scheming, Kibito was sceheming, there was an alliance between Orochi and the sand village, there was a team of super elite badasses out and about in the world… there was stuff going on and it all seemed to have a goal.
7. Everyone had techniques, but they were still ninja-ish. They were all kids training and growing up and changing and working together, all getting about equal development time. They all got better as the series progressed and formed stronger bonds. A story point of emphasis was that with hard work and training, you could suceed at your dreams.
Theres more, but all in all, it WAS a good series. Now, those points have all fallen to nothing.
1. The series still has gratuitous training arcs. Except, there was a time jump, that SHOULD have counted as a training arc. At the end of it, the entire cast seemed pretty much exactly the same. Wheras before had the satisfaction of Naruto pulling off Rasengan, in THIS half of the series, we gfet an experianced adult saying "Wait till you see how much more incredible Naruto has become." Followed by him falling flat on his face. And then beating the enemy with the exact same trick.
2. The two dozen side characters have fallen off the radar. Sasuke and one villain at a time have been the only focuses for nearly two years now. Even the TITLE character Naruto only appears maybe once every 6 chapters for a handful of panels. Let alone Kiba, Hinata, Rock Lee, Choji, etc. The side cast that was once balanced so well, while making occassional appearances, has not shown up much at all. Most of them didn't even have their new designs revealed until 80 chapters into the new arc. Its well and good to spend a few chapters focusing exclusivley on one character, but when ALL the others are ignored as a result, for hundreds of chapters, that were one balanced so well, its annoying. Even Saske, who is CLEARLY the lead character at this point, even HIS team is getting shafted. We haven't seen Team Snake in how long now? After spending like 10 chapters assembling them? (no great loss, but if the main character's own team has fallen to the wayside...)
3. As the series has shifted into focusing on Sasuke, the balance of romance,fighting, intrigue, fanservice, and generally, any given chapter unveiling a little bit more about the world and the characters has fallen apart. The series is almost entirely fighting, and then characters standing there talking. Not even recently, as far back as Naruto looking for Saske, entire chapters were spent just walking and eating ramen. "Developments" that earlier in the series, would have been handled in three panels. Also, the humor that used to be prevelant, but actually kind of funny, has degraded. Jiraiya's bickering old frog couple is just one example. The cuteness of Hinata shyly encouraging naruto and being encouraged in return, or the rivalry between Sakura and Ino, are little character defining things that no longer really occur, between ANY characters.
4. The fights are not as thought out as they were. Itachi and Saske doing FAKE moves while standing still for 10 chapters is just the latest example. As far back as Sakura and Old Lady fighting doll guy, it was like 10 chapters of very repetitive back and forth, just doing the same thing over and over again. And some of the fights that side characters (who as previously noted are getting shafterd) are skipped entirely! Plus, a bunch of 14 year olds are going around slaughtering THE GREATEST NINJAS IN THE WORLD, in one on one fights. In incredibly stupid ways generally. Naruto kills a guy by using the same exact run straight on trick twice in a row. Orochimaru, after having an epic fight with Naruto, dies in a staring contest with Sake. Pein's sidekick is beaten in one panel hen Juraiya SPITS on her, after being set up for an entire chapter. Jiraiya, one of the three supposed greatest ninja alive, has an incredibly dull fight to the death, full of moves we had already seen many times, accompanied by unfunny frogs.
5. The art is NOT consistently well drawn, and is most often, lousy. Every once and again, Kishimoto wil do a really spectacular shot that proves he can do it still, but then the rest of the time is incredibly lackluster. Entire chapters of head shots with no shading or variation in pose are incredibly dull in both composition and actual artistic rendering.
6. The intrigue is gone. The most recent chapters have revealed crucial surprise plot twists that the entire series has hinged around, that have been neither really surprising or interesting. Naruto is actually the son of the fourth hokage and there was a plan all along to give him super Kyuubi powers? Itachi wasn't actually evil but doing it for everyones good because a different member of his clan was being evil. Pein is fueled by the worlds anger! These developments and twists all pale compared to the Orochimaru/Sand Village conspiracy to overthrow the Leaf, the dychonomy of Gaara's monster demon inside him compared to Naruto's, or even Orochimaru's scheme to get Sasuke.
7. Even after three years of training, everyone is still on pretty much the same level. Naruto has, after a time ump and another trianing arc that ONLY he could do (100 clones training at once) has managed to come up with a Kyuubi form he already had that he can't control, and a stronger variation of the Rasengaan he already had that he can't control. (Really, is having three bodies make a fireball more interesting that two?) As for everyone else, well, we haven't seen any of them in acton, so its hard to tell. The idea that was once there however, that with hard work and training, you could suceed at your dreams, has fallen apart. Rock Lee is very lkely NEVER going to win an on camera in the manga fight, since he has no curse seal/magic eyeball/monster demon inside of him. Even Lee is actually a bad example because he has gates and drunken mode. There seems to be no forward progression for anybody despite massive ammounts of time and training arcs having passed.
8. And just because it still bears pointing out, Choji took a suicide pill, foughht to his death in a noble battle and got great death symbolism including butterflies and whatnot, stayed dead for like 4 volumes of material, anf then lived.
And thats far far too much writing, considering those that agree will just go "Yeah", and those that are blind will go "I think its good despite that" without actually countering anything I just said.