I suppose by 2005 I'd come to think of myself as more a casual fan, and certainly one who, unlike Levine, would much rather the show be true to its previous spirit than its letter. In that light I suppose I'd bought into the Paul Cornell new age view of the show (namely that dogma was the root of all evil and misery, and the show was better off without it - I was quite hardcore in that belief then).
So it didn't bother me when Rose and End of the World toyed a little with the lore and only took some of the vagarities of the old canon. That the Nestenes were now a refugee race rather than an intergalactic empire, or that End of the World didn't quite align with Earth's fate in Trial of a Time Lord. I accepted that not everything could possibly be adhered to, and that some things were going to be changed for simplicity's sake. And I probably wouldn't be troubled by the canon being reset back to how it was in its 1977 prime, before everything got messy.
I also think it didn't necessarily bother me that there was meant to be a romantic hints going on between the Doctor and Jabe. The idea seemed to be that under the right writer and story, that could work (ditto, Girl in the Fireplace). I was never that bothered by the romance in the TV Movie. It didn't seem out of keeping with Hartnell's romance with Cameca in The Aztecs, or the hands-on nature of the Tom and Romana pairing in Season 17, or indeed the moment in Talons where Tom's Doctor seems briefly besotted by Leela's Victorian make-over. In the hands of the right writer, those nuances and desires of the Doctor can come out.
Gallifrey's destruction seemed a potential upping of the stakes, and a good way to dump a boatload of excess continuity in one go, so the show needn't be held back.
On paper I think when concerning the new series I was exactly the kind of easy-going fan the Fitzroy Tavern crowd insisted was the best way to be. But then these fan types always love to play the false moderate.
The fact is that as Series 1 and 2 went on, the more apparent it became that RTD just wanted to bait a reaction constantly by going for the wrongest characterisation of the Doctor as a common yokel thug and a lothario again and again. RTD seemed obsessed with the idea this was going to be prodding some feathers, and that the fans would get angry. And I just don't understand why you would have such a belligerent and nasty, petty attitude to your own audience?
It wasn't the romantic inclinations that made RTD's Doctor seem unDoctorish, it was his almost caddish, jack the lad, response to being snogged by a Cassandra-possessed Rose with "Yeah still got it", rather than worrying what's wrong with her. In what universe was that the Doctor? And he only said it because RTD was laughing his fat head off at the idea of how objectionable fans would find it. Likewise Eccleston's thuggish threats to the Editor and hostile jealousy towards Adam in The Long Game.
That's when I was infuriated by the seeming idiocy of the approach. If the Doctor wasn't going to be a more enlightened figure than that, then that pretty much seemed to defeat all point of bringing the show back in the first place.
Another point that annoyed me was in Aliens of London, when the space pig flees, and the Doctor orders a military cordon. The fact that the Doctor didn't even think to yell out "don't shoot!" before the tragic inevitable happens, just made the Doctor seem really stupid for the purposes of the scene. It was plain insulting. And indeed seemed to completely ignore his long history with the military and experience of what they can be like at their worst.
I struggled to square the cockney yokel characterisation of Tennant with the intellectual Doctor of old. But I could somewhat believe maybe in there was the essence of the noble Doctor, buried and compressed like diamond.
I think however it was Moffat's era that really caused the deal-breakers. And ones that would fit under the category of 'sacred cows I didn't realize I actually cared about until they were tampered with'.
Fitting an extra unseen 'War' incarnation of the Doctor between 8 and 9. I didn't think that would bother me. A number's only a number, but it did matter. This pointlessly changed premise that upturned previous assumptions in a way that just wasn't as interesting as the set-up it had replaced.
Then the gender-bending. I always thought I disliked the idea of a female Doctor because it was a bit too novelty, and also I liked the Doctor being someone I could identify with and look up to as a male, and in this day and age, why take that away?
After all I didn't exactly balk at the physics of it in Curse of Fatal Death or various fan films that tried the idea.
But then when Missy happened, I realized it actually has far-reaching repercussions to establish it as just something that was always possible. That the Doctor's prior male regenerations can all be retconned as a fluke each time. It doesn't add up as believable at all. Adn as a result I couldn't invest in the show anymore. It had been changed to the point all meaning had crumbled.
Likewise when The Witch's Familiar made a ridiculous retcon of Davros' childhood and Dalek history and nature, it was just one less reason to care. One less reason to invest in a lore that was now changeable on a stupid whim and meant nothing.
So ultimately I started relatively fine with letting some cows be slaughtered, but now I'm just depressed.
EDIT: One more thing.
I know Jon Blum once went on some nauseating self-important butt-hurt rant about how fans who don't like the celebrity hero worship Tennant was subject to in Planet of the Dead among others, are somehow indicative of the desire to cut the 'tall poppies' like him and Cornell.
But on reflection I've come to realize that what actually bothers me about that cultish hero worship, is I can't help think the Doctor of old would've been genuinely *horrified* that humans worshipped and deified him in such a slavish, undignified way. He'd want friends to like him for who he is, but to still have some individuality and capacity to think for themselves and question him. This I think he would find unnerving. But Tennant just seems to lap this pathetic display all up.