This was sold as a Spanish Fargo, and apart from the Minnesotan snow being replaced by Castilian sunshine, it is so similar it could almost be a remake. We have loveless marriages, normal people getting involved with drugs, likeable hitmen and small-town caricatures.
The problem is the tone. While both the film and series of Fargo functioned as a drama leavened with blackly comic moments, Matadero combines its Fargo-esque style with broad moments of physical comedy which owe more to Hot Shots or Naked Gun. Three scenes in particular, one with a character called Montanas, another with a deacon making a phonecall at gunpoint, and a third with a fight scene between Pascual and Vasco, were so stupid I almost gave up on the show.
Elsewhere, a romantic storyline between two cops approaches soap opera at times. especially with the choice of music, and Fermín, the boss of Alfonso's wife, is such a stereotype of an oily salesman that I don't think he has any place in such a show. I also see his storyline as a common custom in Spanish dramas and films: to pack in extraneous subplots which only really serve to add to the running time.
My final problem, perhaps a bugbear of mine in many dramas, is the credibility factor. My enjoyment of a drama is in inverse proportion to how many times I think "You would never do that". Even if the context is extreme, like Breaking Bad, there can be at least an internal plausibility to the show. Matadero is full of moments where drugs and money - the show's two most obvious MacGuffins - are carelessly abandoned, and many action scenes suffer from a James Bond-style, "Well I'm not going to kill you just yet" attitude.
If you are interested in seeing shows from around the world, or want some Spanish practice, it will serve those purposes. But nothing else.
A footnote: I was sad to hear of the death of Filipe Duarte, the actor who plays Vasco and who also stars in El Tiempo Entre Costuras.