shouldn't be so quick

IBDW spent years trying to make it work. Working on a Sheik for Marth wasn't a rash decision, and it's annoying to see it characterized as such.

recovery is possible with a spacie

Mango is a straight up genius at recovering, and Zain missed some easy stuff (which may or may not have been the result of hesitation because of how good mangos mixups are). Spacie players can certainly learn a lot from how Mango recovers, but that applies to basically every matchup he plays.

it's a different matchup

That's why the answer is no. For FD specifically, no amount of grinding will give Fox anything like Falco pillar combos, and most of his openers (wave shine, drill, up-air) have easily SDIable counterplay. The punish game was never the issue anyways; IBDW's main complaint was that he felt the neutral game requires consistently outplaying Marth in situations where the risk reward skews heavily in Marth's favor. On that front, according to the Slippi stats yesterday, Mango got 31 neutral openings from laser. What is a Fox player is supposed to learn from that?