The point at issue wasn't whether it could be defined objectively.
The point at issue was whether a person could dislike the show because to them the writing is bad.
Playing the "let’s not pretend Star Trek in times past has been uniformly brilliant" card is a straw man. Heck, since I wasn't claiming that bad writing could be defined objectively, bringing that up is also a straw man.
Also, my post did not represent an attempt to enumerate the ways that I think the writing is bad. It was a declaration of the existence of that angle of criticism. The discussions I have participated in in which that topic has been materially discussed better represent my thoughts on it, and I certainly wasn't intending to recap them.
My response was a general one based on, as I said, something I’ve seen from many critics of the series. I just find it kind of meaningless if people don’t elaborate on why they think it’s “bad writing”. Taking a series I’m not a fan of, I’d never simply describe Voyager as badly written. It had some good writing, but I’d explain why I thought the show never believed in or capitalised on its premise, how network meddling made it unable to utilise much serialisation or to move beyond the sense of being “TNG 2.0” and I’d explain how I found the characterisation inconsistent with many characters poorly utilised. Whether people agree or disagree it opens the door to discussion. “Bad writing” doesn’t unless people can take a second to explain what that means. That’s all.