I think you’ve missed the point that it wasn’t the entitled fan outrage that got them the suit, as Jimbo was alluding to, but that the suit was always intended to be given out as free DLC, regardless of how long it has been ready/in development for.
I’m also confused how teasing a costume they’ve given away for free is stringing people along for cynical marketing reasons. If they’d done it then gone “Here you go, $5 please!” then I’d see your point, but Insomniac getting literally nothing out of this, it’s just goodwill for the community. No one is going to go out and buy the game purely because some ugly ass costume is available in it now. Everyone who wants this suit owns the game already so I fail to see what it had to do with marketing.