Or there can be some serious changes to the band lineup which end up making it shit. Examples include The Pogues (without the perpetually drunk Shane MacGowan, they're nothing), The Who (without Keith Moon), Led Zeppelin (without John Bonham), Genesis (without Peter Gabriel), Pink Floyd (without Syd Barrett and Roger Waters), Beach Boys (without Brian Wilson).
However, on the flip side, there are bands that have done remarkably well with a lineup change. These include Massive Attack (post-Tricky sounds better IMHO and in disagreement with silentdan on "Mezzanine"), The Cure (many lineup changes here!), Depeche Mode (with the loss of Alan Wilder), R.E.M. (with the loss of Bill Berry).