They haven't won anything yet. In the cap era, Lou hasn't been able to get a lot done. Eventually drove the Devils into the ground with an aging roster. Left Toronto quickly. Now the Islanders have that same aging type roster, with term on the contracts, so they have to start getting something done.
Not easy finding another Stevens/Niedermayer/Brodeur trio.
Last few Devils years were rough, definitely inevitable with a series of bad drafts. I'd disagree with the assessment that Lou's teams didn't do anything post-lockout. If you're simply judging by Cups, that's a little unfair. The playoffs can be a bit more random than we like to acknowledge.
2005-06: 101 points (won division)
2006-07: 107 points (won division)
2007-08: 99 points (2nd in division)
2008-09: 106 points (won division)
2009-10: 103 points (won division)
2010-11: 81 points (Murphy's law season, bunch of injuries in first half, had a great record once everybody was healthy)
2011-12: 102 points (unexpected playoff run)
2012-13: 48 points (Parise leaves, Kovalchuk mentally checked out after spending the lockout in Russia)
2013-14: 88 points (Kovalchuk leaves, Brodeur given too many starts with Schneider on the roster)
2014-15: 78 points (Lou replaced by Shero)
Not as much postseason success, but it could have been worse losing Niedermayer (and Stevens) post-lockout.
2015-16: 69 points (Lou inherits a 68 point team, begins the rebuild)
2016-17: 95 points
2017-18: 105 points
With Lou, I'm not even sure if it's a pure talent assessment thing with him. He sets a certain tone up top and while some players dislike it in the moment, a lot of them seemingly thank him later on since they needed a certain structure to succeed.