2010: Steven Moffat becomes showrunner
After four stellar seasons and a year of specials, Russell T. Davies stepped down from running Doctor Who. He was replaced for Steven Moffat, another long-time fan.
One recurring theme during Moffat's tenure as showrunner was death. Major companions could and did die—frequently. However, these characters rarely stayed dead, leading the show to occasionally suffer when it came to stakes.
Matt Smith Years (2010-2013)
When Davies left Doctor Who, David Tennant went with him, marking the start of a new age in the show's history. Though it continued the naming conventions of Davies's era, Steven Moffat had very few cross-overs with the earlier period of the show, except for his own character River Song, who had been introduced in series 4.
The new Doctor was played by Matt Smith, the youngest actor to ever take on the role. When he began, he was just 26. Nonetheless, he quickly attracted fans of his own, including many younger viewers.
The Eleventh Doctor had an outwardly goofy nature, though he also had some of the show's darkest moments. For two and a half seasons, he kept the same companions in Amy Pond and Rory Williams, the couple that eventually became the Doctor's family. The extended arcs of each season had to do directly with these companions and their family.
Romance became a much more prominent part of the show, which contributed to the show gaining a strong modern fanbase. After all, there were popular relationships and a few love triangles to keep the fans arguing online.
However, Amy and Rory left in the middle of series 7, and Matt Smith finished his run shortly thereafter. Before he was finished, Smith got to act alongside David Tennant and John Hurt in the 50th anniversary special "The Day of the Doctor."
Peter Capaldi Years (2014-2017)
After Matt Smith, Peter Capaldi was selected to portray the Doctor. This was a surprise for two reasons. First, he was a much older man than his recent predecessors, only a few months younger than William Hartnell was when he started. Secondly, he had already been in Doctor Who a few different ways, playing Caecilius in series 4's "The Fires of Pompeii" and John Frobisher in Torchwood: The Children of Earth.
The Twelfth Doctor began his run by contemplating his own morality, which was something many fans struggled to accept. He didn't attract nearly the same fanbase as Tennant and Smith, but fans found a lot to like in his portrayal looking back.
One thing Capaldi's Doctor was known for was his excellent speeches. From his speech about war in "The Zygon Inversion" to his pleas to Missy (a female version of the Master played by Michelle Gomez) in "The Doctor Falls," he knew how to capture the enduring spirit of the character.
Both Steven Moffatt and Peter Capaldi left Doctor Who after the climactic episodes "World Enough and Time" and "The Doctor Falls" (and the subsequent Christmas special "Twice Upon A Time"). This one again left fans to completely change their expectations for the show.