/u/dandan_noodles gave a spectacular answer to a similar question here, you may find it useful.
In response to your question, the tactics weren't anywhere near as outdated as you might think - advancements in rifling allowing greater range and accuracy were still negated by gunsmoke rendering battlefield visibility low as well as training still focusing on aiming not at individual soldiers but the mass of enemy troops. Most Civil War battles had casualty rates hovering around 20%, with Gettysburg being considered devastating for the Confederates losing around 30% - hardly atypical of this style of warfare, certainly common during the Napoleonic Wars.
Also keep in mind that, despite rifled muskets being able to kill from much further before thanks to their rifling, they were still muskets and could only be effectively and efficiently loaded from a static, standing position, which, coupled with the comparative ease of maneuvering and ordering masses of men by having them in formation as opposed to spread out, in many ways continued to legitimize the tactics and training being used.
Your word choice of "bloody" is vague and can lead to several different interpretations. Are you asking about death/injury rates vs. other conflicts? Death ratios? Deaths in battles? Depending on which you mean, the answer might even just be the scale of the war.
Hygiene was less than non-existent. Soldiers were more likely to survive if they had an amputation to an injured limb (about a 75% survival rate,) a torso wound would likely prove to be fatal. Compounding the issues is that surgeons generally refused to wash their hands. Making matters even worse, sepsis was rampant, laudable pus was something that was something that was spread among the wounded, and it was felt that the pus was something good and should be spread. Confederate surgeons often rebuked advancements in medical technology and preferred to work with the "good ol' boy" style.
This all added to the poor diet (on both sides, but more on the Confederates,) and lack of proper medical training made many wounds fatal.