If that's true, it sounds like companies have been weaponizing the legal system to get access to proprietary information from their competitors. Surely that has got to be illegal somehow?
As it gets more and more weaponized the slow arm of the law will move to prevent it.
The legal cost aspect is unfortunate. However, as others have mentioned, the court probably doesn't require the assembly of new documents, but rather submission of existing ones. So while there is a cost, it's not devastating.
The interesting question is whether or not this specific subpoena has real merit, or if the court was played by Meta.