As a Liverpool fan for nearly 60 years, I'm certain that now was the time - as happened with several Keegan, Fowler, Owen, Torres.......they were never as good for new clubs as Liverpool had made them play.
I hope that Luis is an exception, but while he's the most versatile of his Red predecessors, and new team mates, it just may not work for Barca unfortunately - though it probably won't be for lack of trying on his part