"Well, that's their problem, not mine."

He doesn't say it in an aggressive or unpleasant tone, just matter-of-factly. Maybe one day he'll rejoin the team, he might even help if there's ever another worldwide crisis (let's be honest, those are pretty common these days), but for now he just can't do that again.

"There's a new team now, isn't there? I'm sure they'll do fine without me."