The big problem with the new series compared to the old one isn't acting or writing but format. The old shows were 4 to 8 30 minute episodes per story. For start that means there has to be more story than the current 1 hour shows. You had more room for character development, the Doctor would meet new people in each story and you got a chance to know them more and gave the writers more chance to explain their motivations. You also got a cliff hanger every week which built up the tension more than is possible with current format. There was a sense of time passing between each episode which made the show seem less like the Doctor defeating the Spuggles in 15 minutes. You had more opportunities for things to go wrong for the Doctor or him to be wrong about what is happening.
The new series is good and has some talented writers and actors, but the BBC in hope of selling into the US market went for the 1 hour with ads format. Which in fact gives only 42 minutes of time once you have taken out the credits and adverts. Its tough ask to pack each week a new setup and resolution in that time and get the same quality as the old series. It has done it on occasions, the The Empty Child being a case in point, but not consistently.
The new series is good and has some talented writers and actors, but the BBC in hope of selling into the US market went for the 1 hour with ads format. Which in fact gives only 42 minutes of time once you have taken out the credits and adverts. Its tough ask to pack each week a new setup and resolution in that time and get the same quality as the old series. It has done it on occasions, the The Empty Child being a case in point, but not consistently.