Well, as B&B and ENT bashers go, I can admit to being one as much as anyone...
I'll also admit that I was highly skeptical about the whole premise of ENT from the beginning. However, I did watch most of the first season before gave up, so I did give ENT a fair chance.
The problem with ENT isn't really that it's set in the past. I might not have liked the idea, but I probably would have come around to it if it had been remotely interesting. ENT is particularly interesting to me, however. In fact, it isn't even good Trek. The vast majority of episodes seems to be endless reruns of the same old Trek plots we've seen again and again.
Like I said, the problem isn't that it's set in the past. The problem is that it refuses to stay there, what with time travel, Ferengi, Borg, etc...
If ENT wants to take place in the past, then it needs to establish itself within that past and set up a framework of what is going on. Obviously humans and vulcans are all around with Andorians making the odd appearance, but we hear very little of other later members of the Federation such as Tellarites or Centaurans. Or how about Bolians?
ENT badly needs a background to play itself against, but it has nothing but cold, empty space. That doesn't make for a very interesting premise. And the Temporal Cold War is thrown in there only so often.
Now, this could be due to the desire for episodic shows where there is little or no connection from one episode to the next. But try looking at the popular shows on screen today. Take "24", for example. 24 is serial and complex that you'll have no chance of making head or tails of what is going on if you miss an episode. And that's one of the hottest shows around today. If B&B want a fanbase for ENT, then the episodic approach is the completely wrong way to go because viewers just don't care about characters and shows that hit the reset button when the end credits roll every week. I mean, everybody will be wondering what Jack Bauer will have to endure next week and how he will survive the current crisis, but none will about Archer because he and his crew are quite fine at the end every time. Not much suspense there.
The really bad thing in ENT is that B&B seem to insist on seeing internal continuity within Trek as a limitation to their creativity. But continuity can be wonderful if used well, and sadly most shows use it much better than Trek. Take a look at Worf's history during TNG and DS9, for example. Worf's impact on the Klingons has been profound to say the least. In TNG's "Redemption" it is clear that Gowron would never have been leader of the Klingons if not for Worf, so it is bitterly ironic that Worf ends up having to kill him in DS9's "Tacking into the Wind" so that the Federation and their allies can win the Dominion War. But note that it is more than just ironic. After all, in that episode Dax reminds Worf that the Klingon Empire deserves to die if people like Worf are willing to accept leaders like Gowron. The significance of that is that Gowron would have been killed long ago if not for Worf, so doesn't he have some responsibility for the situation Gowron has put them all in? The point is right there and cannot be easily ignored... oh, and it would never have worked if the writers hadn't played heavily on the established continuity. And that's just one example in Trek.
Another example I like is in TNG's "The Drumhead" where Admiral Satie carefully uses Picard's background against him, particularly his assimilation by the Borg. It's a very minor point, but within attention to the show's continuity it wouldn't have been possible because there would have been no other way to signal to the viewers just how far Satie was willing to go to destroy her opponents. Just making any old comment about Picard's past wouldn't have been as effective because we wouldn't have known the story from Picard's point of view, and obviously twisting the circumstances and the truth to suit her purposes is the very point of the episode.
There is very little use of any such background material in ENT. No, obviously you can't reference things that are yet to take place, but many socieities and much background data has been established in Trek that might have been used. We could have seen Archer and his crew struggle with some of the problems that no longer exist in Kirk's time or even Picard's. References to the T'Kon empire or the Iconians would be just as relevant in Archer's days as at any later time. For example, we could have seen story take place on the nice planet Drema IV. That would have been a bit tragic to those of us who saw it's population die in TNG's "Pen Pals".
Not all ENT episodes are terrible, of course. My favorite so far is "Dear Doctor" because it actually does what ENT should be doing - it explores the principles of what will one day become the Prime Directive. In Archer's day there is no Prime Directive, so when faced with a dilemma he cannot casually pull the Picard routine and quite the Prime Directive. But it is interesting to watch because the episode establishes the validity of a principle like the Prime Directive. In TNG the PD is almost always a major problem, so it's pretty interesting to see a Trek show where the crew is in trouble because there is no such rule. That's the sort of stories ENT should be aiming for. Sadly it does it only very rarely...'
"We think we've come so far... Torture of heretics, burning of witches - it's all ancient history. Then, before you can blink an eye, suddenly it threatens to start all over again..."
- Captain Picard, "The Drumhead" (TNG).