Well, who made the commentary? Were they enlightened so the would understand the true meaning of the original teaching?
Do they need analyse a text that hold the truth? And the explenation is it a personal understanding or the understanding of the teacher/founder of the spiritual path?
It think this kind of question and insistence that the founders or the "originals" were so much better equipped to provide wisdom is a kind of trap that a lot of people easily fall into.
Look at it this way - in any given generation of individuals, there seems to always be a large portion of people who look at the surrounding,
modern human populations with contempt - because they can literally witness, in real time, their fellow humans falling down, doing wrong, and generally just being idiots.
You don't get to see your forebears/ancestors doing this. And so, generally, this tends to have people viewing the peoples of generations past in a better light - thinking they were perhaps more virtuous, didn't do as much wrong, weren't as stupid. But, unfortunately
they very likely were. There were still idiots, there was still a lot of failing going on, and it wasn't much different than today except perhaps that our daily issues and concerns weren't as compounded as they are in modern times.
And I truly believe that it is the abstract, unknowable nature of the "spiritual" that allows it to continue to
always seem "better" coming from times past - but that is really all it has going for it - it's inability to be known for sure. All other actual, practical disciplines that I can think of
heavily rely on updates to knowledge - the experience of those people before us honing, shaping, and indeed
changing the behaviors of those practicing in those disciplines today. I mean... just imagine if those engaged in the discipline of
medicine REFUSED to update their core of knowledge, and it had stood the same for 2,000 or 3,000 years. People would be DYING all over the place - just as badly as they did those thousands of years ago, and of things that are relatively simple to cure or resolve today. The base of knowledge of
medicine is ALWAYS CHANGING. And this is a GOOD thing. That religion doesn't or rarely changes is a hallmark of its complete lack of practicality. It has almost no ties to reality - and so there isn't anything to compare it to in order to definitively state that it is "wrong" or that it needs to be updated because it is currently failing. Oh... and when someone DOES point to something that seems entirely wrong or outdated, there are nothing more than excuses presented to try and cover for that deficiency, or no one is actively practicing that outdated/foolish tenet of the faith anymore anyway.