The approach has changed. Castle fell apart at the end for reasons other than Beckett and Castle dating. And Bones proved once and for all that in the hands of competent writers, a married couple can function successfully on television.
Granted, a certain amount of plot fodder is lost when the couple get together. When Castle and Beckett got together, jokes were issued about the couple "jumping the gun" in comparison to Bones and Booth. Castle and Beckett got together at the end of Season 4, Bones and Booth agreed to date (in the future) in the middle of Season 6. While Castle ended in Season 8, Bones lasted until Season 12. So, in fact, both came together mid-way through their series.
Keep the couple apart, more soap opera material! Fail to get the couple together, extremely irritated (and sometimes disillusioned) fans.
Watching Season 2, I figured out why. In Season 2, (a) Jack is only recently divorced; (b) Jack is still coming to terms with Phryne's free-spirit; he admires her but he isn't sure he can keep pace.
The consequent separation and uncertainty are, therefore, entirely believable. It would take an older, wiser Jack to accept Phryne completely and without reservation in his life: a man who could say, "I'm lucky to have this relationship with this woman."
The problem isn't the time gap between Season 2 and the movie. The problem is that Season 2 has energy and trajectory. The romance is moving in a particular direction--not hurried but without pause. Season 3 halts this movement and even turns it back on itself.
Suddenly slowing down the relationship for no reason that dovetails with the characters' personalities is irritating because it feels manipulative.
I suppose there are couples in real life who continually circle each other--but generally speaking, people move on. When they don't, the failure feels convenient, not organic.
