Suffice to say, the final episode of "Castle" was a Frankenstein monster. Wondering whether I was alone in finding the whole renewal/Katic/"Castle, P.I."/alternate ending mashup utterly lame, I went surfing. Turned out, I wasn't alone.
3) Beckett was an autonomous character. Yes, Castle had the mother and kid and the show had his name, but Beckett was a character. She wasn't just there to enable Castle's creative fiction. She wasn't just there to be an inspiration for a male writer. She's not an embodiment of male fantasy. That's what the ending makes her into. It completely sells out her personhood in much the same way a certain Fox series dispatched with its female lead earlier this spring by making her into an instrument of male deliverance and undoing everything about her as a character. The conclusion of these eight years of TV should not have been, "Oh, that Beckett. She totally inspired Richard Castle."
-- Daniel Fienberg/Hollywood Reporter
Yeah. Moreover, the producers didn't really do an "alternative ending", of course, merely grafted on an extra arm and leg to a body run by an Abby Normal brain. When the Katic firing was revealed, yet with renewal still unstated, I concluded that ABC/Castle's producers were buffoons. Cut costs by firing one of two co-leads? Not only that, but Beckett was the course through which 99.44% of the stories flowed. (Which, not incidentally, would be good reason for the actor playing the titular character to grow a tad fractious with his co-lead. Just sayin. Wouldn't you?) Castle, the man, would do a De Niro and jump into bed with Hayley and consult with Ryan and Espo now that beloved Kate was hors de combat? Is there any credible segue? Nope.
So, it is clear that the ABC/producers had no idea about an alternative. "Bring me the head of Kate Beckett!!" must happen. Or both. The cliffhanger had already been shot, evidently. Shooting a new ending really means writing a different, completely, ending, then filming it. A Jack-in-the-box Caleb was tawdry anyway, so I suppose that, being cheap and lazy, they merely tacked on the most saccharine ploy from a Creative Writing 101 class does track. Which is to say, a classless ending.