nor does it excuse him doing nothing but pitying himself in 'Destiny'.
Ah yes, so no one is ever allowed to pity himself, not even when he has been mentally scarred beyond what even he thought had been done. Starfleet training should allow him to overcome anything?

Remind yourself of that next time you're feeling a little depressed.
If the Starfleet guys must always surmount any odds, which do we keep reading ST fiction? Give the guy a break. The Borg is Pcard's Archilles' Heel. He has a unique empathy for the Borg's assimilated drones. He's already permitted the killing of thousands in "The Best of Both Worlds" and tried to make a moral decision in "I, Borg" (and "Descent"), and tried to fix the situation in "First Contact".
Maybe Picard should have sought retirement due to trauma long before this, but then he's hardly a worthy "star" of such an epic story, and it took "Destiny" for anyone to realise the true depths of Picard's injuries. "Destiny" is what it is. You didn't like it, fine. You'll never change your mind, or David Mack's, or the sales figures. But you'll never change our minds. Stalemate. Move on.