When It comes to the slice of life genre, I feel there are two main appeals(aside from straight moe/fanservice). The relaxing vibes or the rich character dynamics.
If Yuru Camp is the golden standard of the former, I think Hyouka would be my pick for the best of the latter. A show that is carried solely by its characters, this is both why I love Hyouka while others hate it.

Hyouka's premise is kinda boring at its core, four friends, one genius, mysteries, go; There isn't much to bite into if you look at the premise itself, and this can grate on many people looking for a more attention-grabbing show.
I don't feel the same way, but I still have to dock points in the story department because even I can see how at times it seems like the plot refuses to move forward. If this show doesn't grab you, it REALLY won't work, which isn't common in most anime.

However, if slow but realistic character growth and mysteries click with you, this will absolutely be a treat to watch. Yonezawa Honobu is a master at using his characters in the best way possible.

At its core, Hyouka is driven by its characters instead of an overarching plot. Oreki, Chitanda, Satoshi, and Mayaka play off one another in the most compelling ways possible. I find that these characters are compelling because of how realistically they're portrayed. We see into the small details of their lives and how they struggle with grounded, realistic things. We see them change, little by little, with their worries about where they may be headed. Hyouka's characters skim the line between dynamic and stagnant, quite similar to how most people live. But when a character changes, it feels that much more impactful since we know their usual habits in detail. The audience feels what that change means to him/her. The realism of these characters draws us to them, inviting us to want to know more and see them grow. If these character changes were the sole premise of the show, however, it would turn out to be boring. Thankfully the show's many character interactions are framed around its mysteries.

These mysteries are inordinately small in scale, giving the characters more room to express themselves since they're not dealing with a life-or-death murder case. Oreki's pointless and amazing conversations with Satoshi wouldn't be welcome in a higher-stakes story. But here it serves to give the puzzle even more flavor. This is where the hook for the mysteries lies. by themselves, the cases have little excitement or energy to keep the audience with it. But the characters and their personal involvements make the audience care enough about these well-plotted but slow mysteries to look into them alongside the main cast. Hyouka might be missing exciting action or high stakes, but it more than makes up for it in its characters and how they interact with the mysteries.

This isn't to say the mysteries aren't engaging in their own right, but it can be hard to sell an audience on the "mystery of the locked door".The detail of the cases is where they shine. They may be simple in stakes but they are dense and well made, Each one gives the audience enough clues to figure out the mystery by themselves, but create such complex situations that it feels cathartic when Oreki can piece together both the theories of the other characters and the audience. But Oreki is no Holmes and none of the other characters are Watson. Every member of the Classic Club contributes in their own way to solve the case which lets them shine in their own way. Mayaka serves as a reference point to keep the other characters in check, Satoshi is a reliable database that the rest of the characters can consult, Chitanda drives the mystery forward with her enthusiasm, and Oreki is the one to put all the pieces in place.

The mysteries, small in scale as they are, serve a secondary purpose. That being the worldbuilding of Kamiyama High School. This takes us through the school's troubled past and its lively present giving us a complete picture of all its eccentricities, most notably its massive number of clubs. By the end of the show, I felt that Kamiyama was a real place that the characters had just begun to explore.

This is helped in large part by the astounding animation quality that makes Hyouka feel wildly different from much other anime because of its consistent attention to detail. Small things like background characters being almost as well-drawn as the protagonists and the constant attention to the time of day/weather make the show seem extremely believable. I usually expect periodic dips in quality as the animators try and save their time/energy, but there are no blemishes to be found throughout. It gives Hyouka very high-production energy which I love. The sound matches this quality, all the voice actors are expressive and seamlessly melt into their roles, and the animation is often enhanced by background sound effects when the animators want to add emphasis or draw attention to certain details. I might have issues with the first ed ( as many others do), but the rest of the music is solid.

All this contributes to a plot that I think stays rock-solid with few or little holes during most of Hyouka's runtime. In the final few episodes though, some issues rear their heads. After the conclusion of the festival arc, the most exciting and impactful of the show is followed by a few episodes of events that can be described as basically plot-irrelevant. When I read reviews calling Hyouka boring and uneventful, these episodes are often used as examples. Now I think these episodes serve a great purpose, though they may be uneventful they finalize each character's overall growth throughout the series. It conveys how the characters return to normal life, and normal life isn't exciting all the time like during one of the major arcs. But even a well-done plot shift in the last 4 episodes can be jarring.

All these complaints are only made worse after watching Hyouka's inconclusive ending. Being an adaptation of a currently unfinished light novel, an incomplete ending is inevitable. But for a show so focused on its character growth, seeing it go unfinished hampers its overall quality. The conclusion works well but does nothing to bring it to a true close that an audience can be satisfied with. This is especially apparent when it comes to Satoshi and Mayaka's characters, who only get a few lines of dialogue in the final episode dedicated to them. All this makes finishing Hyouka a much less enjoyable experience for many compared to the beginning and middle of the show.