They are almost certainly not accurate or complete. The details in the article come from the defense attorney that the shooter hired. According to the article, the defense attorney hasn't received the police reports yet and even if he did have the police reports, he is not obligated to provide the media with an accurate account of the details. Also, especially recently, the media isn't in the business of providing non-biased, complete, and accurate information.
It is pretty likely he will not spend any time in jail. The DA filed this case via a summons, rather than a warrant, so he was not arrested and jailed on the charges. I have no inside knowledge of the case, but it wouldn't surprise me if a deferred judgment or a misdemeanor with no jail was offered. With that said, assuming he was convicted as charged at trial, it is a class 5 felony and is punishable by probation up to 3 years of prison. Simply put, the judge is not sending this guy to prison for accidentally killing his buddy. Based on the charges, it is clear he doesn't have a felony history. If he did have a felony history, he would be charged with felon in possession.
This is what negligence means in Colorado - "A person acts with 'criminal negligence' when, through a gross deviation from the standard of care that a reasonable person would exercise, he [she] fails to perceive a substantial and unjustifiable risk that a result will occur or that a circumstance exists." Criminally Negligent Homicide (otherwise known as negligent manslaughter) is the same level of felony as breaking into someone's car to steal change. Sure, none of us want to get charged with this, but it is not like he is getting thrown in prison for decades. The charge is for the exact kind of conduct that appears to have occurred here. You ask, wtf good is charging him? If filing the charge results in people who hear about this tragedy pausing and making sure they are not blasting their buddy, it is probably worth it. That is one of the purposes of the law - deterrence.
Finally, you mention cost to the public. I imagine there are upwards of 100,000 felony cases filed in the state of Colorado every year. This one case will not really cost anything. The DA's salary isn't dependent on a little case like this, the Court and Judge will be there with or without this case. Sure, there are costs associated with trials, but unless the DA or defendant are totally unreasonable, this guy will come into court in a few months (maybe longer with COVID) and he is going to cry his eyes out because he shot his buddy. He is going to plead to a lesser or a deferred, he is not going to jail, and he might do some public service. Who knows, maybe he will speak at hunter safety classes as part of his sentence.
In the end, this will probably end up being a tragic cautionary tale with minimal criminal consequences.