Yeah, there's a major difference between a department with a half-dozen writers and half-dozen editors and probably several dozen to a hundred or so alpha testers all trying to cross every T and dot every I, versus thousands upon thousands of people all reading simultaneously and finding edits and broken combos. Especially when the internal people have been seeing the same documents for months on end with constant changes happening to wording and sizing (especially when these pages have to be edited to fit inside pagination and around art correctly). A couple words removed by a layout editor so it can fit on a single page all of a sudden unknowingly takes out a key component or restriction of an ability-- and other editors don't catch it and it's the morass of the player base that says "Hey wait!"
And the thing is... more often than not all this "errata" only occurs and is known by players because they are all online and can see it gathered all together in one singular place... making it seem like it's a big deal. But I guarantee you... if this all occurred prior to the internet and each of us was at home flipping through this book ourselves, we might notice like maybe one or two things that were technically wrong if that, and most of all the other stuff would just go flying right on by us. And we'd never even realize just how many things might technically be mistakes.
Easiest way for a person to not get upset about the amount of errata? Just don't read threads that other people put together that bring them all together. Because you can't get mad at things you yourself don't ever notice.