I'd agree DS9 is the best Trek but it shouldn't be held as the standard for Trek casts. It's the only one without a bland void in the main crew. Not a Sulu, Dr. Crusher or Harry Kim in sight.
Voyager is a hugely annoying show for many reasons but The Doctor, Seven of Nine and Kes are all great characters. Replacing one of the few good characters with another good character is one of the most frustrating things in all of Trek.
Voyager is frequently dumb and mediocre but people exaggerate how bad it is. Mainly because it had the potential to be the best series.