Mobile Defense is one of the few functional commanders in this game.
It augments the core faction in very meaningful and supplemental ways. It counters specific stock allied strategies.
Just because theres not a large community of people trying new strategies to keep the metagame fluid doesn't mean that the existing metagame is wrong or even problematic.
Because what, are we looking at a situation where light vehicle rushes are a problem for axis or that having light vehicle rushes countered a problem for allies?
You know, its quite hard to come up with new strats, when balance moders make sure the moment you do something new, its slaughtered by nerf bat, because new = op.
Heavy tanks could be best example here, they used to be dominant meta, sure, but nowadays there is no single situation where 1 heavy would be better or even comparable to 2 meds for effectiveness.
USF is pidgeonholed into 2 strats, both resolve around light vehicle rush, UKF got only single BO and they still are slaughtered, the moment you do anything else, you failed because anything else was nerfed out of the game.
OKW, same as USF.
Sov and wehr have most freedom here, because they both are generalist armies who do not have and massive holes in their armies and are not balanced around gimmicks.