This is what I'm worried about, too. I think River was a great character because she was first imaged when RTD was at the helm and the Moff was one of the writers. I think both of these guys have flaws, but that together they made something really good with her character and back story. Amy was initially a good character when she was the little girl who waited for the imaginary man from her childhood. I don't know what to make of her, but I'm kind of glad she's gone since I think her character ran out of steam a while ago. I hope the new companion is more like early Amy, or Donna. Amy's personal story was wrapped in the overall plot and that's something I think Moffat does well. And Donna could go toe-to-toe with the Doctor without being, essentially, a female version of the Doctor who could do anything, which is the feeling I get from this new companion.
Honestly, I'm not really a fan of River. I thought she was really intriguing when she first showed up but she's just been handled so strangely that I don't have any real connection with her. With most other characters, we see into their lives a lot and we get to know them. Since River was made out to be ~SUCH A MYSTERY~, we never got that with her. Even in episodes where they reveal all sorts of her secrets, they're always just "plot point A and then plot point B but don't let that settle in for long because PLOT POINT C SURPRISE!!!" We never get time to sit and think about her and then every appearance she has, she's just all-knowing and practically omnipotent. Like the Doctor except she never explains anything and instead of an explanation she just flirts and it's... it's really annoying to me. :( But again, I think this is just Moffat's writing because iirc a lot of the River-centric episodes were written by Moffat himself instead of handed off to other writers.
Definitely agree that the new companion feels really doctor-y. Like, so far the only character flaw I've noticed from her is that she... dies a lot? I guess we haven't had a whole lot of time to examine her and get to know her but considering the treatment of characters (especially female characters) since the head writer switch-off, I just find it so hard to have high hopes for her. I feel like if they don't give her some actual defining traits, she really will just become a second River which is redundant.
This is exactly why I liked Donna too, and the same with James Cordon's character. I disagree about Rory though, I reckon he'd stand up to the Doctor a lot more if Amy wasn't around since it'd be more of a power struggle between the two males whereas when they were travelling as a trio, Amy was pretty much in charge of them both haha. This was the main thing that I started to dislike about Amy, the show became all about her at many different points where I'd prefer it to focus on the Doctor and them saving planets etc. They took her way too far, especially with the whole "infertile --> divorce" situation that arose - that kind of stunned me that they'd actually go to those extremes haha.
Rory doesn't really like the Doctor. Mainly because of Amy, I think, but he's just... I dunno. I can't imagine him actually going around with the Doctor for more than an episode or two on his own. He doesn't really want a part in any of the danger and really only seemed to stick with it because he was married to the Most Important Girl In The Universe 2.0 and that's what she wanted to run around doing. :/ He just never had much chemistry with the Doctor for me. But I agree that Amy became too much of the focus and that's why I'm so glad the Ponds are gone. I liked them but I didn't like their plots and I HATED that Amy was such a focal point for the entire series but... we learn almost nothing about her. I can't really name much of anything that she liked/disliked, I don't know much of her history, I don't know anything about her dreams (her becoming a model, making her own perfume, etc... I didn't really see a connection between that and anything that had been shown to me prior, for example. I mean, I had no issues with it but it just seemed so random). I just can't understand how a character can be so very important yet so very bland when you try to dig deep down.
I was fine with the infertile thing. It was interesting, even. Devastating! But the fact that it came up and was resolved in... what... 2 minutes? That was ridiculous. Factor in that we had no idea the Ponds were having problems before that episode (unless we watched the Youtube short prequel which, let's face it, the majority of viewers didn't) and the fact that the whole thing takes only one episode to fix--and the Ponds don't even fix it themselves, really, it's the Doctor who pushes all of it--just irked me so much. I think it could have been a really emotional insight into Amy and Rory's relationship, being able to see each other as equals and learning to talk things out properly... and we don't get any of the impact or any of the sympathizing feelings because it's all so abrupt and before we can even process they're having marital issues over a serious problem, it's fixed and wrapped up nicely with a bow. Okay. I had a LOT of issues with that episode, haha.
Jack was amazing, yes! But the Doctor never seemed to like him much, he kept treating him like he didn't belong which was disappointing - he would've made a great permanent assistant. My favourite moment with Jack was the whole Master trilogy of episodes, his character really shone there. Shame Martha was there to spoil it, the rest of the episodes/cast were amazing.
I think he warmed up to him in the end but I guess he still kept him at quite a distance throughout, which is a little unfortunate. But I still think Jack was a good influence when there was someone else there. Sort of took the edge off the (often annoying) sexual tension between the crushing companion and the Doctor. Plus, he knew his way around time and space while still being modest about it. Well. Sort of modest. Sometimes. Ish. :P
Aww, Martha. :( I really wish she hadn't had such a crappy series to star in. Immediately after Rose was just the wrooong time for her and she just got the short end of the stick in so much of that series. She was awesome in series 4 and because of how much her character developed, I think she's my second favourite of the main companions in NuWho. But ugh do I ever wish she hadn't had the unrequited love story.