The anime and manga had something going for it, but it drops the ball. It's a narrative clad in a bourgeois revolutionary doctrine. The setting is feudal and that impacts the MC by influencing the decisions he makes. He's there to rock the boat, though not by his own volition, so his mere presence threatens the existing order. The shield hero is a heroic archetype caught up in the role of a scape goat. They will always inspire the masses (or beastmen) to revolt, so the monarchy accounts for that. It doesn't particularly matter what the shield hero does, however it just so happens that the shield hero is a merchant. Historically, the move from feudalism to capitalism was progressive, but in retrospect it becomes a fantasy when depicted in any other context. The MC is this self-centred misanthrope whose actions are a means to an end. He trades, buys slaves, and takes advantages of poor villages not in the best of conscience, however he always does in his ethical framework. He has taken his alienation and channeled it into a position of power. It's all about turning your weakness into strength.
Describing it in this way, there's a premise that can be done justice, but I dropped the series and others I have talked to have done the same. It isn't just a problem with the anime, but the manga also suffers from some problems too. It's very obvious that the waifu bait is a key part of the series, but it wasn't properly contained. The fact that Raphtalia went from a loli to a full blown woman was bullshit. It skips character development and the change is jarring. Fillia is forgettable. The tone gets watered down. That's all obvious. My problem is that the conflict with the monarchy is too contrived. Once the queen was revealed I dropped it because the lure of a conspiracy just disinterested me and by then the show's edge was gone.