Possibly because you loved the old series so much? I didn't. In fact, I only liked bits of it and was never in love with it - and that is the same thing I felt, right from the start, about the RTD era, I have been very critical of much of NuWho and, indeed, gave up watching it over the last full season and most of the specials. But I like this new doctor and this new companion, and this has never happened before in the whole of NuWho.

It's the same way I didn't like ST:TNG or Voyager, but liked classic Trek and DS9 and the reboot... Not in love with any of them, but happier with some that with others.