Moffat made scenes longer as well didn't he? There was less darting about from one thing to another so maybe that was a factor in it seeming tired? I feel like a big difference from Eccleston to Tennant was that Tennant seemed to have a lot more dialogue, especially technobabble, and he was completely at home with delivering it, and with the pace of the series.
I'm not sure, I know he got in a repeating rut this season with "Uh Oh the Doctors in the worst straights imaginable, no way out, oh wait, cue the music, he hops up and starts babbling about being right where he wanted to be all along, never any danger, blah blah blah" they did that so many times on Capaldi's run if it were a drinking game I would have died.
Moffat seemed to be recycling the same premise tired of originality, and Capaldi just seemed tired delivering his lines.
And the stories just weren't that interesting to be honest. there was one where they kept the Doctor in a repeating time loop for like 12 billion years and by the end of it, I felt like they had me that long too...
And I hated Maisly Williams added part on the show... grabbing her between seasons of Game of Thrones just to make her a huge deal in the overall Dr. Who lore as an immortal and all I'm thinking is... she's just a kid.. you realize next year she's not going to be able to pull off the role assuming you can even get her that often...