A lot of it was people not giving it a chance. Instead of feeling like a stand alone show it was made to feel like a TNG spin off while TNG was still on the air.
I ended up giving it a second look and it's become my favorite incarnation of Trek. Unlike most other Trek shows I felt like DS9 was consistently good right from the get-go. And there was so much character development, I felt more attached to those characters more than others just because so much time was spent on character driven story arcs.
And I'm saying this as a lover of all things Trek, but DS9 is just a stand out to me when it comes to story telling.