Holik left to get overpaid (thanks Glen Sather) and we had a kid named Madden who stepped up and helped us win a Stanley Cup, and a Selke trophy.
Gomez left, we got Zubrus a player who helped us battle for the Stanley Cup last season. Meanwhile, Gomez is hated by his current teams fan base because of the stupidity of his current contract (Thanks again Mr. Sather).
Mogilny signed for big bucks in Toronto for a whole 30+ games. Lou picked up a kid named Friesen who played a key role in helping us win another Stanley Cup.
It is always better to wait and evaluate what you have, rather than making a panic move.
Last year was great example of improving as the season goes on.
While I agree with your general thoughts, some of this is revisionist history. Zubrus was blasted left, right, and center by people on this board up until this past season, really. He was producing 50+ points playing with Ovechkin, and many figured he'd put up those numbers with New Jersey... but this past season was his highest total, at 44 points. With the style played by the Devils now, he seems much more valuable.
Madden did replace Holik, true. But when Madden left, Pelley was supposed to replace him... that didn't happen.
When Mogilny left, it was Pierre Dagenais (spelling?) that was supposed to replace him... that didn't happen.
When Niedermayer left, Malakhov and McGillis were supposed to provide blueline stability... and that move damn near screwed the franchise for years.
When Gionta left, it was expected that Niclas Bergfors would step up. He performed well for the first half of the season - and enabled Lou to swing a deal for Kovalchuk. THAT was a great plan that panned out because Kovalchuk was willing to sign long-term with New Jersey. It was iffy until then, though - would have been a lot for a rental that only helped NJ win 1 playoff game.
Overall, Lou's desperation scrambles/Plan B approaches haven't worked that well. That's why I wouldn't be shocked if he took a new approach this off-season and makes an offer to a player like Semin, but it wouldn't be for nearly as much money as Parise gets. Semin made $6.7mil last season, I'd be fine taking a risk on Semin for 1-3 years at $6mil per season.
I'd still prefer a deal to Buffalo, where they get Greene + prospect + 2nd rounder for Stafford... after they ship players and picks to Anaheim for Bobby Ryan.