Whilst I have accused Voyager of villain decay, especially in regards to the Borg, I don't hate that Voyager used them. The Borg were used very well in Scorpion and the concept of Species 8472 was amazing. However, they should've left it there and what Voyager did with the Borg later on Dark Frontier and Unimatrix Zero was terrible.
Same goes for the Q. Voyager's episode "Death Wish" was an interesting, engaging and welcome expansion and exploration of the Q, but it didn't destabilise the Q or ruin them as an enigmatic species. Hell, I rate Death Wish a LOT high than Q's episode in season 1 of DS9 which felt pointless and tacky. It's VOY's The Q and the Grey (and later Q2) that do a grave disservice to the Q.
So basically, I am fine with Voyager revisiting existing Trek species and characters, but they over did it and whilst I am reviewing Voyager to get a fresh perspective, I doubt I am going to change my mind on this issue.