I’d still call this “light” Sanderson, and for that matter “light” Mistborn, if compared to the original trilogy. There’s very little worldbuilding and it even misses that focus on the magic system found in The Alloy of Law, adding little and no longer going into details. In addition, Wax goes from the most developed and interesting character to perhaps the least so. He can definitely fight, making for a few thrilling scenes in a book that also has fewer such moments overall, but that’s pretty much all he is, the hand, the sword, the gun, whatever you prefer, Marasi, Wayne and maybe even one or two secondary characters having much more to offer.
That said, after a first part that quite clearly fits this “light” description, more and more social commentary makes its way through and much of what comes from Marasi in particular is definitely relevant if you think about recent and current events in our world as well, Marasi seeming to take over the spot of the most developed and interesting character this time around. There are interesting bits of a different nature coming from Wayne as well, though he otherwise remains too stereotypical and the fact that the main characters operate separately more often than not means that the way in which they fit and work together isn’t so relevant anymore, which hurts his “value” the most.
Though not at the level seen in The Alloy of Law, the antagonist again has an understandable motivation and makes some valid points, at least once they’re finally revealed, bringing some theological issues into debate as well. And the overall story stands well enough on its own but also seems to lead the way towards something much greater and deeper while at the same time connecting with the original trilogy. As such, if indeed intended as a “stepping stone”, it does a good job, also remaining enjoyable and, at least if seen through the lens of these “lighter” expectations, satisfying. Don’t expect reminders or much exposition, however, so those who forgot important details may need to refresh their memory.