Bleach, you were once considered by the anime community to be one of the greatest shows of all-time. Now you're considered one of the worst.
Let me start out by saying, this was my gateway anime, and it's what got me actively into anime 4 years ago. Despite its flaws, I still love this series, but not as much as I used to for many reasons which I'll get to in a bit.
Bleach is about a high school student named Ichigo Kurosaki, who can see the spirits of the dead, and later encounters Rukia Kuchiki, a Soul Reaper (Or Shinigami as it is in the fansubs) who helps send the deeply departed to the Soul Society, and slays Hallows to do that as well. She later ends up having to give him her powers in order for him to protect his family.
However this is a grave crime in the Soul Society, and Rukia is later taken back where she is waiting execution for her crime. Ichigo and his friends of course then go to save her, and later many in the Soul Society also find corruption, and conspiracies in their system.
This is where Bleach was at its best, the Substitute arc (1-20) and the Soul Society arc (21-63) are what made Bleach so successful in the first place. You had such an action-packed story, with deep elements, and good character development. You could have almost considered the show a masterpiece with what took place in episodes 1-65. Then from there, it went downhill. The first of the filler arcs began, the Bount arc which personally I find to be the best out of all the filler arcs.
Speaking of filler, about half the show is filler. This is all due to Tite Kubo's complete inability to pace, period. Manga readers know full well he doesn't know how to pace. He draws such large of panels, and puts in hardly dialogue (And backgrounds-"Backgrounds in my Bleach?"), it's no wonder why a single episode will cover 3-5 chapters, causing them to catch-up to the manga very often, leading to all that filler.
Now back to where it went wrong, Bleach began to fall apart after the Soul Society arc beginning with the first filler arc, the Bount. The Bount arc did have its fair share of good points (Like going into the extermination of the Bounts, and what they had gone through because of the Soul Society), but it was a letdown at times due to the poor pacing (Yes, even filler had bad pacing, go figure...), plot holes, and the lack of explanations to certain things that need explaining. The other arcs later suffered from these same issues (and from a few Dues Ex Machinas), and the character department began to suffer as well.
The arc that had the most issues was the infamous Hueco Mundo arc which dragged on and on, and is by far the longest arc in Bleach. This is where Bleach's success began to wane. The TV ratings became shit to the point later on it led to the show getting cancelled after the Fullbring arc, people were dropping this series left and right, it lost its "Big 3" status (Note: If you still believe Bleach is "Big 3", you're either ignorant or behind the times) and more.
The characters of Bleach are what the fans love the most about the show. Many have such cheesy personalities, deep backstories, and the usual desire to protect someone. However one character that really stands out as being bad is Orihime. You cannot turn a blind eye to her. After the Soul Society arc, she becomes almost completely useless (The only use she really ends up having aside from that minor support for her friends is healing people), whines a lot (Ex: "Kurosaki-kun!!!!!"-Oh look we ripped off InuYasha, not just YuYu Hakusho (Spirit detective) and Hunter x Hunter (Clan extermination, you being the only one left-Uryu-and wanting revenge against who did it)...) which is the reason why so many people cannot stand her), and has her development go completely backwards as she becomes a damsel in distress, and willingly no less.
The others will suffer from the same issues at times. For example Ichigo changes as he realizes he's not able to really protect what he loves most, but then will go backwards back to where he was at times by being scared of his own power. He'll also keep being the blind idiot that'll charge towards every opponent without ever really thinking things through.
Now's not to say the show doesn't have any good points after it goes downhill. For example, you still have the desire to protect, an intricate plot with Aizen and what he was planning to do with the Hogyoku, what does it mean to be human, and the issues of exterminating something you created. But with Bleach's many issues after the Soul Society arc, it fails to ever be as good as it once was. It's a shell of its former self.
The storytelling issues just leave you scratching your head at times, causing you to not be as deeply involved with the show as you once were, the characters having messy development also causes the same issue, and more. This is where you find yourself not loving it as much as you did.
The art and animation comes from Studio Pierrot, who does not do a very good job with what they do with production values, even today, but this is where they did it that best. The artwork looks rather nice, and it's not the typical art you'd find from your average Shonen. The animation can be awkward at times (Especially during fights, and running scenes), but it can be rather nice.
The sound is just good, the characters have good voice actors (Both sub and dub), and the background music fits in with almost every scene, but some tracks leave much to be desired.
Bleach in the end is a show that started out truly great, but later went downhill, and became a shell of what it once was. It's still very good (Barely, just barely), but not the near-masterpiece it once was.