They were on the other side of the galaxy. Many expected aliens that were "totally different" -- whatever that means. Incredibly huge, or with bizarre physiologies, or something. Intead, we generally got the same "forehead aliens of the week" that plagued all other Star Trek shows. Heck, the Kazon were basically Klingons on bad hair days.
There was Species 8472, which was quite different. And I suppose that running into The Borg made some sense. But what else did we get that was truly alien? The giant "virus" which made no sense. I'm trying to think of others.
Also, I read an interview very early in the first season wherein the powers-that-be mentioned the obvious pitfall to avoid, the "Gilligan's Island Syndrome". Each week, they'd encounter some unexpected way to possibly get home, but it would always get botched. Okay, they didn't do that every week, but I seem to recall a few episodes that more or less fell into that category.
In the same interview, they mentioned that hopefully they'd go five to seven seasons, during which time, while the distance seemed insurmountable, there would also be a feeling that they were making progress the whole time. A reason to keep hopes up. I think we got a shortcut or two, which was good. Too many would have been silly, so they had to strike a balance. But overall, it just felt like they spent seven years going nowhere, then suddenly at the end there was a miraculous, unexpected break, and they took it. Ta-da, we're home, fade to black.