Anytime you have a collection of update active, competent people you basically have the formula for coordinating and demolishing opponents.
Hyper coordinating attacks, update activity, massive warchests, knowing how to maximize damage, and being super active basically gives any collection of nations with similar NS a huge damage advantage over their opponents (especially when many of them are MIA for days at a time). That there is no ability to down-declare on DBDC is basically icing on that cake.
The reason why no one will be able to touch DBDC indefinitely is there aren't enough competent and active nations in that nation range to collectively counter them.