Every Trek series has its haters. It’s just Deep Space Nine, Voyager and Enterprise get a lot more hate because.
Because? I dunno, because haters gonna hate.

Deep Space Nine got hate because 1) it was a Babylon 5 ripoff, and 2) the cast was stuck on the station and didn’t go anywhere (such people didn’t watch during the Defiant years).

Voyager got hate because 1) it was a TNG rehash, 2) the captain was female, 3) it didn’t challenge cultural norms 4) it didn’t have a major story arc with the renegade terrorists that are the Maquis, 5) it nerfed the Borg.

Enterprise got hate because 1) It was on UPN and not everyone had UPN; 2) it had several callbacks to the other series rather than standing as its own show.

Also, apparently plenty of people seem to think Rick Berman held the franchise back by not rocking the cultural boat.