Some of the best tomb design the series has ever seen. Just brilliant stuff. It tries very hard to backpedal on the odd direction TR2013 took the series in, instead focusing on exploration, puzzle solving, and occasional combat, with some nice design callbacks to Underworld. Mechanically very nice.
I personally think the game suffers from very weak writing, and it becomes weaker and weaker towards the end of the game. Writing-wise, even Rise of the Tomb Raider fared better, and that's saying something. Key aspects of Lara's character arc feel bizarre and... unearned. Like, she doesn't feel like a real person as they desperately try to turn her into this blubbering emotionally shattered creature that doesn't know what to do with her life.
It's a shame because the game's actors are kinda decent. The themes the plot tosses around are interesting. But gosh, they're so clumsily executed. Even that one scene with Lara and the fire where she starts murdering people felt like a callback to Lara in Underworld when her mansion is on fire and she's in a murderous mood. But it falls so unbelievably flat in Shadow.
Shadow is an example of a game that needed a complete story rewrite. Imagine if FFXV had reached release but instead of the total mess we got, it was an even bigger total mess where every character was Jared.
What's really painful is the live action Tomb Raider movie that came out a year or so ago provided a formula for making the somewhat wonky "nu-Lara" work as a character. Come to terms with her missing father, and the loss of her father. Confront Trinity. Shadow just farts it up the wall. A lot of nifty ideas mechanically, but... okay, I'm gonna be blunt here.
Remember how Thief 2014 was pretty badly written? How the ending felt bizarre and disjointed? Well, Shadow of the Tomb Raider makes Thief 2014 seem amazing, coherent, and emotionally vibrant in retrospect. And that is bizarre to reflect upon.
Long story short, the game itself is pretty good. Mechanically and puzzle-wise it's got some awesome stuff going on. But the plot, the writing... something went really, really wrong.