No, they're actually a good deal more dimensional and lively than the old versions became over the years. These kids are better actors than the old guys - for the most part - and I'm looking forward to seeing what they do in times to come.
DeForest Kelley's
filmography would like to have a word with you.
William Shatner? Not a great actor, but he was great in that role. And what he did was in the style of male leads on television at that time. He owned that role.
Leonard Nimoy? Granted, it took a few episodes to find the character (kind of hard when the writers don't even know who/what you're supposed to be and they're making it up every week), but when he did, he had it locked. His character was reserved, but deep - his calm masking an intensity beneath the surface (Quinto always looks like he's about to yell).
Walter Koenig. OK, not so much.
George Takei was just fine.
Nichelle Nichols. She was OK. Many actresses could have pulled off her role.
James Doohan. A lovable, but rather two-dimensional character.
Yes, the background players were rather shallow, but they were in the background of the trio that really defined the show. It's OK for background characters to be simple, because they provide a simple reference frame for the rest of the action.
We should keep in mind as well that producing a TV show in 1960s involved getting a script slapped together and throwing it into the hands of actors who were still memorizing lines when shooting started.
If you think that anyone could have walked into those roles in the original series, I would refer you to the many fan productions of the original series. The sets usually look OK (at least as good as they did in the 60's). The stories are usually OK. The special effects are much better than the original series. And yet these productions are terrible, because the acting is terrible. Every time a watch a few minutes of one of these fan productions I am struck by how good TOS really was.
RLM ask a valid question of nuKirk and nuSpock's bromance - "Why are these two people friends?" I can't figure it out myself, apart from the fact that Shatner and Nimoy established the relationship for them and that relationship still resonates in our cultural memory.
It's not the fault of the actors in either case. I am not a fan of Pine's Kirk so far, but then again, it's not his fault that thev're written him as a womanizing jock with no regard for duty. I'm sold on Quinto's and Pegg's acting chops. I'll throw Urban in there too. The rest of the cast could be replaced with no harm done.
The talent level is comparable, but the chemistry of the original cast took it to another level. I'm not saying that the new cast isn't capable of generating that chemistry, but it's hard to do that when the characters are involved in general calisthenics and firing hand phasers.