Great explanation right here:

This is the kind of stuff that doesn’t show up on a stat sheet. The block does, yes, but altering shots at the rim, making guys pass instead of shoot, etc – there’s no way to boil all of that down into some nicely-packaged Twitter talking point. Embiid is just more impactful on the defensive end. Nobody is hunting Joel or exploiting him.

The other thing that no one seems to talk about is that offense is always valued more than defense among fans and media. Think about it. We love home runs, slam dunks, touchdowns, and goals. We love those more than blocks, double plays, pass break ups, or clearances. Kids grew up wanting to be Kobe Bryant, not Bruce Bowen, because offense is sexy and defense is defense. That plays a role in how people look at the MVP race, whether it’s conscious or subconscious, and Embiid will always have that working against him.