It seems like everyone at the higher levels of the cartel in Breaking Bad and Better Call Saul is pretty intelligent; in particular, they are smart enough to avoid doing impulsive things that endanger the enterprise. Tuco's crazily stupid murder of No Doze ended up drawing the attention of the police not to mention frightening people who work under him to the point where they might well question why they are loyal to him.
I could see him being an enforcer, but just the fact that he is a user of meth, I would guess would have made his uncle (a terrible person but smart and controlled when he needed to be) not employ him as anything else. Tuco is far below people like Lalo or Nacho or even Crazy 8 intellectually and there is no shortage of violent people (where violence is needed) -- even his loyalty is shown to be in question as he is sort of abusive towards his uncle Hector once Hector has become disabled.