The happy-go-lucky Captain of the first season had me running for the hills. He beams down to a planet with his dog, who gallops around the alien fields oblivious of what little alien bugs might leap onto him. What a total goof. I really felt sad for the Star Trek franchise. I tried to put up with it for a few more episodes but then bailed.
I came back later when I saw previews for the end of season 2 as the Xindi arc started. That changed everything. By then some of the very wooden characters were becoming palatable. Archer realized he had a back bone and started using it.
Some of the stories were really good, but I considered the Borg as "hands off" due to what was established in The Next Generation. They never should have gone down that road. I think it was a serious mistake. The Xindi idea was unique and worked well and the writers should have come up with more story ideas like this.
Honestly, the show did get much better in season 3 and 4, but many of the second tier characters made the show look less than it could have been. Perhaps they needed a little more time. But it was too late. It is a shame, because I think Bakula really got rolling and making Archer work well. He could carry the show, almost the way Stewart did with Picard. Even Blalok was getting better, although I felt the Vulcan depictions in Enterprise were either too emotional or too wooden (few Vulcan depictions in the Star Trek franchise could match Nimoy's definitive take, with Tuvok a close second).
I do think Enterprise could have gone on for at least 2 more seasons if they'd gotten to season 3 momentum by the start of season 2. It was just bad timing.