I just don't think Kimbrel was a failure, any more than Sewald was for the Dbacks, or Jonathan Broxton was for the Dodgers in 2008 and 2009. Every closer but one eventually blows their big save.
And Kimbrel had a very good season. Might have been an even better one if he'd been used less and more open to different roles (and neither of his bad games in the World Series were actually save situations!). And last year's team got to the World Series. Knebel wasn't good and Robertson was an imperfect replacement but the fact that Alvarado had two bad games against the Astros wasn't really the story of the series.
Closers are unreliable and the ones that are perceived to be reliable are overpriced and then become unreliable. Hader is a very good one obviously but his turn will come too, and in the meantime he costs far too much. There isn't really any other sure thing in the free agent market. They'll sign someone - Liam Hendricks? Aroldis Chapman? Hector Neris? David Robertson? Kimbrel himself? - but not necessarily to close. The best thing they could do is find another Strahm.
Last year they signed two All-Star closers (Soto and Kimbrel). The lesson from the last two years for me is that you don't need a traditional approach to bullpen management to have great success, not that a closer would take the Phillies from great success to perfection. And like most things it's better to develop a closer than sign one. None of the other three ALCS/NLCS teams had an experienced name brand closer (which is to say they weren't that when they took on the role).
I'm with Andy on the hitters, essentially, leopards don't change their spots, and some hitters aren't even willing to watch video or work with the batting machines. Should you treat those hitters like Allen Iverson not being willing to practice, or let them continue to do what works for them? Because five games in the ALCS is not the story of Trea Turner or Nick Castellanos's season either (and in Trea's case I believe he finally started hitting once he stopped doing some of what Long had asked him to try).
But... that also means the team really could use one hitter with a more disciplined approach, because none of the three young players are truly that either.