No, he doesn't.

On the other hand, you can play him in a non-JLI deck, and Juggernaut isn't a 7-drop teamstamped to a faction that will never play him for his drop, and there's that automatic Blindsiding Juggy does that Cap doesn't (because Cap is a nice boy you see).

Juggernaut is heaps more playable than Captain Marvel is. Heaps. Try looking past the raw card stats and into reality and you will see this.

Because the Injustice Gang swarm deck has a ridiculously crowded resource row as it is and a teamup only worsens that problem (to say nothing of leaving you open to resource row hate). Because with the Gang's accelerated weenie drop speed, Light frequently exhausts out their biggest drop when it matters most. Because there are other ways to deal with Flame Trap and Reign of Terror now.