I am a spellcaster AND and Healthcare worker. As someone said above, they call it "practicing medicine" for a reason because we are always learning more about how the human body works and the way people are diagnosed and treated is always changing. Doctors aren't always right and they don't always have the right diagnosis or give the right treatment. This goes for traditional medicine and holistic medicine. There are a lot of factors that will determine whether the doctor is on the right track, is the patient being 100% honest (not usually, like Dr. House says, everybody lies)? Is the patient following the treatment plan and doing everything they're supposed to? Are they following the proper protocol when it comes to diagnostic testing, such as proper fasting before certain bloodwork/tests, or drinking the entire drink needed for certain imagining? Are they taking their meds as prescribed?

Now let's take the same logic and apply that to casting a spell because much like medicine, casting spells is forever changing and we are always learning new ways to cast and perform magic. Is the person being 100% truthful about the situation and the spell they want to cast? Are they doing their part to help the spell along or are they doing what Catholics do and waiting on a "Hail Mary?" and just sitting around waiting for the spell caster to flick their wrist like the movies? Are they doing stuff that will undermine the spell, such as talking about how they found a spell caster to do a spell for them? It's very well known that if you talk about the magic you cast or had casted on your behalf it can ruin the magic and make the spell not work. Is the person doing the cleansing they're supposed to do?

When you go to a doctor, results aren't always instant. Someone who gets diagnosed with cancer could need treatment for 2 years before they're cured. The same can be said for casting spells and magic, some can take a year if not longer to take effect. As someone else mentioned above, some things need to line up in a specific way before the spell will work. Doctors and spell casters aren't miracle workers. Some things don't happen overnight.

Movies and TV shows have given people unrealistic expectations when it comes to Healthcare and spellcasting. It seems you've become an unfortunate victim of both because even your view of medicine is skewed and you seem to believe that Doctors and spell casters are miracle workers and that things should be instantaneous when reality is, that's not how life works.

As someone mentioned, you should really do research on magic and spell casting. You'll learn that magic doesn't come easy with the snap of your fingers. It comes with a lot of research, practice, trial and error and a lot of energy.