I enjoyed the show to an extent. It was not my favorite anime or isekai but worth watching none the less. Many of the shows problems could be easily fixed like very easily fixed. It is a well-structured darker take on the isekai fantasy that adds some lesser used aspects that are not commonly seen in the genre.

Let's start with the obvious pros.
The most important aspect worth noting about Shield Hero is that the characters actions have consequences. Naofumi having faced consequences for crimes he did not commit but more importantly the other characters such as the other heroes causing problems having lingering effects instead of magically disappearing or the antagonists getting being punished for their crimes.

The show does have clean and strong animation.

The concept surrounding the show is refreshing for the genre. You have four heroes summoned instead of the usual one and as an added bonus they themselves are from different versions of Japan. The main character can't attack and instead must be clever and use the one tool at his disposal and work harder than most isekai protagonists to accomplish the bare minimum. That work eventually pays off. The world is conspiring against him and he earns respect from the people by the end.

The world-building is decent. While it really doesn't bring anything new to the fantasy genre, you can tell that more thought and effort went into using the traditional fantasy stables compared to others of the genre. It is sword-and-socercy so there are things that come with the genre. This is especially true in the RPG Isekai genre. This world has instead of the usual malignant demon has "waves" of monsters. While on the surface this is more original than the standard it doesn't leave a lot to the imagination.

There is a good amount of tension in the story. With Naofumi you never know what he will do especially when it comes to the other heroes. This character trait was established early in the story and continues onward throughout its entirety.

Now the cons. And we'll start with the biggest flaw of the series, the characters.

Once again lets start with the biggest one. The one that everyone brings up. Of course i'm talking about Raphtalia. The slave girl turned sword princess and Naofumi's potential love-interest. To put it in blunt terms, the character was wasted potential and another victim of poor character development. Raphtalia could have been a great character and in many aspect still is. The problem stems not from the fact she was a slave when Naofumi met her but the fact that instead of simply having him go "You're free now little girl" instead he decided to keep "enslaving" her which honestly never amount to more than upsetting the viewers. There is a simple rule in writing that you should avoid doing anything that would take the audience out of the story especially if it has nothing to do with the plot. Raphtalia being a slave was never the problem, the problem came from Naofumi never dong anything about it except the short-lived brooding and questioning about the ethics of owning a slave that was ultimately dropped. I mean she had no where else to go so she was stuck with him either way. The enslavement of the demi-humans was actually one of the more interesting darker aspects of the world the show touched on. Then comes the ultimate isekai sin, she fell in love with him without any real effort. Any good romance has some give and take from both sides and takes a decent amount of time to develop. While love at first sight is an idealistic pipe dream it's not practical in story telling. To Naofumi's credit he did "friend-zone" her so the love is basically one-sided for the most part. Unfortantly Raphtalia's potential as a character is limited to her undying devotion to Naofumi instead of coming into her own individual character. She is incapable of doing anything for herself and while episode 15 gave her some much needed emotional depth, it still doesn't change the fact that her life, even before she met Naofumi, was devoted entirely to the Shield Hero.

Naofumi is refreshing compared to other isekai protagonists. For starters he wants to go home which is surprising uncommon and older than most being that he's 20. But as a character, he is dull and lackluster. Not a blank-slate but can be summarized in two words: "Angry" and "Bitter." He has every right to be angry at the world and the people who tore him from his home, labeled him a devil, and treated him like crap. Unfortunately being sympathetic doesn't make him likable and makes it hard to root for him. He comes off as appealing as a cactus and treats everyone like dirt whether they deserve it or not. Instead of being more rounded and having some charisma he relies on anger and often indifference to progress through the story. Even at the times he proves his worth as a hero or the only adult in the room, it comes off as a negative because of his overwhelmingly negative disposition. The saddest thing about his character are the moments of positivity that shine through on occasion that make a world of difference not only for his character but the show overall.

Filo was/is pointless. There was no need for her to shapeshift and while she does have some use as a tool and animal companion, her own devotion for Naofumi comes off as weird and unhealthy especially in human form especially when Raphtalia already holds that spot. If you took her out and replaced her scenes with Raphtalia or god forbid another character, there would be no difference. There is no problem with her as a bird to pull the wagon or help fight but as a girl and a full party member, she does more harm than good.

The Three Heroes started off interesting and engaging but as the show progressed each one devolved into incompetent replicas of one another that lost any individuality they may had once had and any potential they could have gained. This leads to a secondary problem because while the show continuously preaches that the four heroes must work together, Naofumi continuously has to work solo without them because not only his lone-wolf nature but because they are beyond incompetent to the point their inclusion in the show becomes nothing more than decorative.

The lack of variety of characters is another problem the show has. While not a real harem it is still harem-esqe. This once again stems from Raphtalia's lack of personality and Filo's unnecessary shapeshifting. Like both those things, sadly this could have been easily avoided by simply having a male party member and Raphtalia being more independent.

The story and animation while decent in its own right lacks finesse a lot of the time. Moments where small changes could make a world of difference if scenes were edited differently, shown more, or had the characters express more emotion either through facial expressions or body language. Naofumi's own battles rely heavily on using his own anger which is a common thread of the show, but lacks consequences at this point other than vague foreshadowing and warnings. The concept that there will be consequences for using this power is worth noting, it doesn't matter if we don't see them affect the plot. The times creating and strategy are used, they are quickly brushed aside to let Naofumi use his superpowered shield to win the day despite the fact that it is heavily emphasized the importance of corporation with the other heroes and Raphtalia herself.

All in all the show while not great earns its spot in the upper class category of isekai anime.