As you posted yourself it's matter of taste, but I for instance simply can't stand another "Gandalf come and save the day" situation because everyone except very good authors heavily abuse such tropes.
I perfectly fine with this kind of stuff in something like Discworld because of nature of these books and how I read them, but for epic fantasy with more or less serious themes I expect events to have logic behind them. Sanderson's books still have mysteries, but they just served by the ways other than generic "magic". So there is plenty of things to make theories about during and after reading.
Yes, of course, it's a matter of taste. I can't argue beyond "I like reading this and dislike reading that".
Ultimately, to me, literary fiction is NOT like programming, and it's not as easy to explain what works and what doesn't. Mystery and ambiguity are bad things in code but good in literature.
Which brings me full circle to why I dislike Sanderson's approach :)
I perfectly fine with this kind of stuff in something like Discworld because of nature of these books and how I read them, but for epic fantasy with more or less serious themes I expect events to have logic behind them. Sanderson's books still have mysteries, but they just served by the ways other than generic "magic". So there is plenty of things to make theories about during and after reading.