Here is what I think. Season 1, 2 and 3 sucked big time aside from a few off flow episodes such as carpenter street of Detroit or the one where they found a wild west human colony. This isn't a Quantum Leap show
Season 4 was great.
Don't get me wrong I didn't hate season 2, 3. It just didn't have what takes to be classified as "Star Trek" No diplomacy no nothing. If the xindi threat was like fluidic space species it would be better. Xindi should have appeared here and there. Not all the time. Attack on earth was far fetched. I don't recall anyone ever mentioning such an attack.
I think they tried to mix elements of TNG Voyager and DS9 which don't mix well. Nothing weird happened aside from three episodes (although the sub -pace virus was hardly how a traditional weird episode goes, it was just a set of flashbacks) as it used to in TOS. No wierdness such as a non humanoid alien doing something at all aside from ONE episode.
I think we had a season of or less good episodes. The start of the serries was f***ed up as well. It starts with suluban, a species we have never seen in the serries. Enterprise should have normaly left space dock. Although vulcans role was made fine.