I agree that it'll take time but if they're going to try and ape what the previous group did then the show will fail. Its stupid for them to even try and stupid for people to be expecting that either. They need to do their own thing, and be themselves. The only thing they should try to keep is the high production values and a variety of car interests (so new stuff, old stuff, weird stuff, supercars, interesting locations). Let the chemistry happen naturally.
People forget how awkward Clarkson/Hammond/May were for quite a while (several seasons before they really got into the swing of things; actually May wasn't even there the what first season?). They made the same mistake I was talking about as well, as early on they aped the previous iteration of the show a lot, and that stuff was mediocre and boring and really comes off as filler. Hell even after 20 seasons they still had segments that fell completely flat.
People definitely need to keep things in perspective (and especially the people making the show).
We'll see how things go, but it sounds like Evans has been a bit of a backstage disaster so far. I'm also not sure about the others (Harris and Sabine would be great but I don't know how well they'd hold up to doing a regular show, especially if they have to try and ham it up and can't be natural).