The most complimentary thing that this supposed Sturm exposé could say about Garrett is that Garrett was a middle-of-the-pack coach that didn't catch a break for 10 years...and that would be farfetched because we had so many self-inflicted wounds that it'd require a damn near 'miracle', not just a 'break'
Yea, the only argument is that he's basically just an average NFL HC, which may be true, but there's also definitely an argument that he's solidly below average.
The long and short of his tenure in my opinion is that he rode Romo/Dez/Witten to very mediocre results from 2011-13, then saw more success (but still very uneven success) between 2014-19 primarily thanks to the fact that our drafts improved significantly over anything we had seen since Jimmy, presumably thanks to Stephen realizing that Jerry had to be marginalized after trading up for Claiborne in 2012.
How much of a part did Garrett play in marginalizing Jerry in the draft room/personnel decisions?
Nobody really knows, perhaps he deserves credit for that as well, but nobody can say with any certainty what sort of role he had in that.
The reoccurring theme throughout his entire tenure was that the team often came out unprepared in the biggest moments (Green Bay 2016, run defense against the Rams in 2018), generally seemed to lack football common sense and could never sustain success from year to year.
The only times Garrett-coached teams ever had success was coming off disappointing seasons where expectations were low, and then every single time they followed that success up with yet another disappointing season that failed to meet expectations.