I totally agree, Neelix didn't go anywhere. He is supposed to be the gypsy of the Delta Quadrant yet settles in more easily than the Maquis and doesn't want to really go anywhere or achieve anything. Not that all characters have to be dynamic, guys like Paris should and guys like Tuvok must stay the same.
Perhaps this structural problem of the series has something to do with Janeway. Like many women who started to occupy hitherto male-dominated positions in the 80s and 90s Janeway was often "more man than men" (don't call me a male chauvinist, women noticed this "Thatcher factor"' as well: And so, watching as our women have moved into leadership roles, I noticed that, initially, to get into those positions, the women were trying to be more men?more male than the men. And there was a stridency and an anger in some of those early women leaders, which is understandable.
- Jane Goodall
) and often very maternal which is why she is often criticized as a decentered character. As any challenge to her authority would have made it necessary for her to be even more male it was impossible to have any Chakotay-Janeway rivalry concerning the "throne" in the first season or any other strong characters which includes a better Neelix that isn't satisfied with cooking or playing morale officer.
Note again that this isn't a sexist point, if someone like Jadzia Dax had command she would be more relaxed and able to endure strong people besides herself.
About T'Pol, the problem was often lack of subtlety. Take the Trellium addiction stuff in Season 3 and the ensuing romance with Trip. Why humanize her like this and in such a soapish manner when Blalock can, to use your words, "give off emotion without being emotional" perfectly fine like e.g. in the sublime final scene of the series
(for me Terra Prime and not These Are the Voyages... is the proper end of Enterprise)?
So I guess I have rather an issue with the writing, if she gets a good Nimoyesque scene (in your sense of showing feeling precisely via not showing any directly) she can play it nearly as well as Nimoy.
By the way, this subtle style is similar to how Spiner played Data although the difference is of course that Vulcans have emotions but show little of them whereas Data is ontologically split: he is not supposed to have emotions, he clearly has none in a "neurological" sense but it is nonetheless obvious* to everybody that he has feelings (unless you really wanna argue that he just emulates human behaviour when he works like crazy to save his dieing daughter). He might express something like friendship fairly technical ("As I experience certain sensory input patterns, my mental pathways become accustomed to them. The inputs eventually are anticipated, and even missed when absent.") but so what, it is not like he is a complex sentient machine whereas we are complex sentient machines plus some unknown X. Our unknown X that arises out of biological complexity is our consciousness (not just unknown but not knowable, you cannot explain consciousness scientifically as science always seeks automatic mechanisms which is the very opposite of consciousness) and Data is conscious as well so his basic paradox, that he has feelings although he has none, should not surprise us.
* - An exaggeration, I know that unlike the fairly ordinary point that Data often appears to be more human than we are my claim is quite controversial as it is not merely about how Data appears to us but about how he is.
About the technology, just like there is some not-so-obvious serialization in the form of subtle themes running through the show such that you gotta watch the entire thing from beginning to end to appreciate it we also had to wait until one of the last episodes to really see that 22nd technology looks more primitive than 23rd century technology.
This is the tragic paradox of ENT, it only works retroactively, e.g. the nasty Season 1 Vulcans only make sense once you have seen the Vulcan three-parter in Season 4. But by then the ratings were already down and reacting too sluggishly so the series was canceled ... and then everybody watched the last season in reruns or on DVD and loved it (and the folks who did not love any of the gems in S4 need to spend some serious time in a reeducation camp near the Klingon-Orion-Federation border