Truth be told, I was more affected by the news of David Tennant leaving the show than I was by the news of Matt Smith's exit. 10 will always be the Doctor that redefined Doctor Who for a whole new generation of viewers, after the reintroduction of the series by Chris Eccleston. So for all intents and purposes, 10 was a tough act to follow.
Not that I didn't like 11, mind you. Smith brought a freshness, a meanness to the show. He brought a tense edge that wasn't there during Tennant's jolly old doctor. 11 was a world-weary Doctor with a young face, and the contradiction worked amazingly at the start. His affection for both Amy Pond (Karen Gillian) and River Song (Alex Kingston) were genuinely touching and powerful, to the point that 11 once again redefined the show, bringing in an art house experience, introducing the viewers of shows like "Before Sunset" to the quagmired love story of the Doctor. This desire to introduce both Pond and Rory Williams (Arthur Darvill) to the wonders of the universe blunted the edge that was ever present around Smith, and occasionally brought him to the root of what it meant to be the Doctor.
And yet, that wasn't enough, apparently. As his inverse history with River Song came to a head, the edge of this Doctor turned into a quiet desperation. It was good for the most part, since it was logical that an old man nearing his death would take milestones such as meeting his future / past wife heavily. But the biggest problem with Smth's characterization of the Doctor came about when showrunner Stephen Moffat decided to "kill off" Pond and Williams, and effectively turned 11 into a brooding, antisocial hermit not unlike Batman.
And that's where the series, for me, ended. When the angels took Manhattan, and sent Rory and Amy back to whenever it was. That ended the season for me, and despite my best efforts to get myself interested, anything after that I met with lukewarm reception, at best.
You see, it didn't look like Moffat planned for anything after Pond's exit - and neither did Smith. The overarching storyline devoting the rest of the season to the development of Clara Oswald (Jenna-Louise Coleman) was simply not enough to get me invested in the character. Everything about the series was bland when the character was introduced, to the point that I hoped Oswald was actually the next big bad guy, maybe the newest incarnation of the Rani. Alas, that was not to be, with Moffat instead relying on the deus ex machina that ended the last season.
Now, I like Stephen Moffat. I love his writing, and I had great expectations for him as showrunner. And, for a time, barring greatly anticlimactic season enders, he delivered. But I couldn't help bit think that perhaps one of the reasons Matt Smith is exiting early is that the chemistry built by Moffat between him and Pond was meant to last a lot longer than it did, and the story went so haywire after she left that Smith didn't feel as devoted to the franchise as a result. I cite the lack of character development of Clara, the strange introduction of John Hurt as the Doctor, and the second "killing off" of River Song as examples.
As for the future, with the twelfth - and LAST - incarnation of the Doctor, I can only hope that Moffat and co-showrunner Mark Gatiss make an interesting enough character like 10, who can survive a multitude of broken hearts. Because unless they pull an asshat of a reboot, 12 is our last hope, ladies and gentlemen.