Well, except that, First of All™, Jrue Holiday is a very good defender, and earned his spot on the First Team. And, Second of All, they didn't get in "over" Embiid and Horford because, unlike the All-Rookie Team, which has been "positionless" since at least 2010 (if you'll recall, Tyreke Evans' ROY campaign saw the First Team include four point guards and Taj Gibson, compare that to 2016, which basically ended up being four centers and Devin Booker), the All-Defensive Team continues to be voted on according to "traditional" positions. Which means, by rule, there's only room for one center, and that spot went to Gobert.
If you want to make an argument for Embiid and/or Horford being snubbed, it needs to start with how Covington got the second forward spot over either one of them. Also, quiet as it's kept, Anthony Davis' defense is lowkey overrated as ****. I probably would have put him on the Second Team.