That's an Oberoni fallacy. Just a because a good DM can overrule the bad math doesn't magically fix the bad math. I expect WOTC to be better at math than the average DM, not worse.
No it isn't because by the rules as written you aren't supposed to be using the math in the first place. It's as if we had rules for holding your breath under water, and a paragraph that says "if you're not under water, you don't need to roll to hold your breath". You're arguing that it's an Oberoni fallacy for me to argue that the breath holding rules aren't broken for holding your breath while in the vacuum of space because according to the rules, you shouldn't roll (or at the very least shouldn't be using that system). The skill system is designed to be used to resolve checks where there is a "significant" and interesting chance of failure. What is an interesting and significant chance of failure? By the rules, at least a 10% chance or so.

The problem is, you're looking as the skill system as "this is how skills are resolved, so this is the minimum and maximum chances of failure for all things." On the. Other hand, I'm looking at the rules as saying that "if you have a scenario where you need to randomly resolve a chance of failure within this given range, you should roll the dice like this"

I mean lets be perfectly honest here, almost every scenario that people bring up for how ridiculous the skill system is are almost always ones where no one would roll anyway.