Seriously, back in the days John Siracusa would dive into internal details. For example in 10.7 Lion (in 2011) Apple introduced full disk encryption. John didn't just stop at the usual description of the functionality, screenshots and performance metrics. He described Apple's then-new logical volume manager implementation to get this feature to work. He then speculated on Apple's future plans for the technology (pooled storage aka a single logical volume group spanning multiple physical drives) which became the reality in 2012 with Fusion Drive. This is the kind of review I wanted to read.
'Oh people don't like looking at long documents' - then they're not your target customers and you should just ignore them and stop listening to the ad sales person who is paid by commission.
I recommend the excellent EclecticLight blog (by H. Oakley). He doesn't try to do a comprehensive overview (you have Ars for that), but has done many technical deep-dives covering changes that haven't been talked about anywhere else, and I can't praise him enough for that.
Michael Tsai also has a great blog (mjtsai.com/blog/) that functions as a news agregator for Apple stories and commentary, and though his blog's not dedicated to only macOS, you'll find regular stories on technical details there.
(I miss John Siracusa's reviews for ArsTechnica)