ENT had plenty of great ideas in its first two seasons. A minor one was to elaborate on the Prime Directive and how humankind slowly learns that human moral and interspecies ethics are two pair of shoes. The most important one was to use the concept of the Federation not being happy family from Journey to Babel. The slowly developing friendship between Archer and Shran is indicative of how the entire Federation slowly forms out of mistrust.
Ironically the nasty pre-Reformation Vulcans who were partly influenced by Romulus pissed off a lot of fans. So when the show feels too familiar it sucks and when it dares to change some things it sucks as well. Some people can never be satisfied.
Talking about innovating familiar aliens, we have seen the the honour concept of a Klingon lawyer and doctor. After so many Klingon stories it was about time to show non warrior-class Klingons.
About allegorical stories, ENT did not have more or less than any other series before.
Oh, don't get me wrong, I agree that ENT has some decent-to-good content, but it also did have a lot of reused content and some very bland content.
I'll take bland over silly (looking at you, 70% of Voyager), but still.
The Human-Vulcan-Andorian relations was indeed the best of ENT, along with, as you said, those Klingon episodes; but the formation of federation ethics and alliances was very sparse before series 4.
They mostly focused on the
technological birth of the federation, rather than the
socio-political birth of the federation in s1/s2... and that's not enough to justify the premise.
Technology is there to serve the story, not the other way around.
(and it did have less allegorical content than say, TNG, at least intentionally so)