I remember really looking forward to Enterprise for a number of reasons:
1. I thought Bakula was a great choice for Cap'n.
2. I loved the idea of going backward since Trek got more and more sterile as it went forward in time. And the idea of a prequel to bridge the gap was too enticing to ignore.
3. I was dying to see new weekly adventures of a ship called Enterprise again.
But too many decisions were made which turned me off initially (I have since found many reasons to enjoy all 4 seasons). In the first place, the choice to not include the name "Star Trek" in the show's title was a misstep which served to alienate many fans. Then, of course, I remember my jaw dropping at the placement of an easy listening song as the main title. It was an appropriate song (lyrics-wise), it was just not the adventrous sort of "to adventures bold" kind of music I was expecting. That damned song got the brunt of criticism from day one.
Like most latter day Trek shows, the pilot episode was great and not reflective of the season to follow. There's something about the dozen episodes following a Star Trek pilot that is just amazing to see. The concept in the pilot is beautifully rendered and great fun. Then, it goes into slow, meandering and tech-heavy exploration. Plots were taking the form of gimmicks (Trip gets Pregnant! The crew turns paranoid!) and the really poorly done and very dull teasers didn't help either (Archer falling down in the shower is not my idea of an exciting situation). Voyager lost me early on this same way ("there's coffee in that nebula" says the addicted Janeway). There was little energy, but this show should have had it in spades. It was about astronauts truly going where no one had gone before and all we worried about was Hoshi being afraid and what Malcolm's favorite birthday cake was.
That, to me, is what killed the fanbase. A great start and then a dull thud. It took too long for the show to deliver on its promise. And the whole "it takes three seasons to get good" crap is just an excuse. Not only had this producing team been making Star Trek for 14 years and should have had it down pat, it didn't take TOS three years to get good. It was good from the start.
By the time Enterprise found its voice, it was too late. But it was soooo good by then.