I have recently started watching the Star Trek Enterprise from the start, and while watching it, I have realized that even though the acting was not at par with what the viewers had gotten used to, like in TNG or for that matter the original Trek, I really do understand as to why the acting fit like a glove specifically in Enterprise.

As the first Earth ship to venture into deep space, there were many episodes as well as situations that had been dealt very easily in TNG and voyager earlier, but they couldn't have been dealt with in Enterprise the same way. Like the idea of a prime directive. No such directive existed before Enterprise. So when you watch the crew deal with new situations like that, their raw, and sometimes crass acting gives a tinge of reality to the series (albeit a small one).