Do I think most private companies could defend against Double Dragon or Lazarus or Fancy Bear? No, if a state level adversary is attacking you and the payoff is that good, you are going to get popped.
But a strong posture makes it harder, which means they throw more at you and you have a chance of picking up on the attack. Best case, anyways. Worst case, you get to testify to Congress that your security measures were top notch and industry leading. That sounds a shit ton better than “we left a screen door open and didn’t notice for months.”