He had an utterly forgettable season in totality This is false. Nico was one of the three best players for Athletic Club as they qualified for the UCL for the first time in years. He was named to the Europa League Best XI for his performances in that tournament as they made a run to the semis (before a flukey & disappointing elimination to a scrub United squad, with Nico missing the 2nd leg anyways). Obviously, he's still performing for Spain whenever he's in action. He performs better in the Spain squad than he does in Athletic Club, because he's playing with more attacking players in a more attacking system. And still, he stands out among Athletic Club players in most matches, because he's really the only player who demands the defense's focus almost every time he touches the ball. He's not a Lamine or Dembélé that will beat double-teams regularly, but if defenses can only send 1 defender at him, he's very dangerous. He already has established chemistry with Lamine, Pedri, Olmo, etc. He'd be a clear upgrade to the attack.

I love Gavi as much as any player in the squad other than Pedri, but 200M is a fee for a top-5 player in the world. If PSG hypothetically offers that insane amount, you tell Gavi to take the money for 4 years and then come back to Barca when he's 24 on a free deal.