Shatner was a solid man in TOS, verging on a little overweight at times - but muscled overweight, not soft overweight. Pine was a bit more 2000s-fit, but not what I'd call slim. Wesley is just a lot slimmer and lanky. I don't feel like he could throw a punch.
I'm not body shaming, I'm the last one to do that. But Kirk as a character keeps himself fairly strong and clearly enjoys a burger (to the point that McCoy has put him on a salad diet before). Kirk 3.0 looks like he enjoys a nice tofu burger. And that's great; he seems healthy, but he isn't built like Kirk should be.