Tl;Dr - everybody on Voyager lacks the most basic of common security sense, and roams the delta quadrant with the naivety of children. Discuss.
Long version: Let me preface by stating that we've watched all of TNG and DS9, and we're approaching the end of Voyager, so maybe I'm just burned out on Trek's writing in general, but why do so many of Voyager's plots require a complete lack of security common sense to work?
Case in point: we've just watched "Repression", wherein Tuvok has been attacking and mind melding with all of the old Marquis crew, who have now all recovered from their mystery comas and been put straight back on duty. Tuvok is in the brig talking with Janeway. Not only did they let him keep his combadge, but when he uses it to relay a bunch of strange words to Chakotay, who replies that he "understood", Janeway at no point thinks it might be prudent to have Chakotay immediately detained. This leads to a full ship takeover and Janeway almost getting killed.
Then literally the very next episode a random trader is able to straight up steal the doctor out from under everyone's noses. I know the internet was in its infancy when Voyager was created and we were all pretty naive about data security, but come on!
So many plots rely on critical systems being wide open for anyone to tamper with, or crew members lacking the most basic of common sense and/or being way too trusting of complete strangers.
I appreciate that it would be a pretty boring show if everything was locked down and people did their jobs properly, and that I might as well be complaining about the fallacy of Holodeck safety protocols, but I had to get it off my chest!
If it weren't for the fact that it's become a bit of a running joke to point out all of the ways a major plot device could've been avoided I think we'd have stopped watching a couple of seasons ago.
Has Trek always been this way, or is the writing on Voyager just particularly lazy/bad?
It's been there since TOS.
It isn't lazy writing, it's the necessity of long term writing for a series.
If you take the tos concept of "wagon train in space" as the starting point, if you want to maintain a multiple season show, you have to explore every idea you can come up with. You discard the ones that don't fit the vibe, or you tear them apart until they do. But you have a deadline, budgets, and an ever-critical audience.
So, you get episodes like the one (s3e8 TOS) being rewatched in that community. A zero stakes illness, some hand wavy tech, and a single episode romance that amounts to a pile of meh. They can't all be winners, and Voyager had and extra limitation in that it was expected to do a roughly TOS journey, with TNG baggage, and still manage to not retread plots too obviously.
It isn't lazy, and I'd argue that it isn't bad writing either, as Voyager usually managed to keep characterization on point and didn't fuck up with major contradictions often.
In universe, you had people far from home, unsure if they'd ever get back, surrounded by strangers and emitted enemies. So the crew slipped a lot. It fits well enough as a head canon that only the really egregiously bad stuff can't maintain immersion.
But it's the nature of series writing. You always run into a "what the fuck do we do this week?" wall. It's really rare for a show to have a long enough commitment that there's real planning involved the way Babylon 5 worked out. Where you can tell the big story and fill in little bits in episodes rather than having to shove little bits of big story into one-off episodes.
I've done some amateur grade serial writing. If you don't start off with the big picture in place, every chapter is a wrestling match between the idea you've got now and how it fits in the long term. It's fucking brutal sometimes. I'm struggling with one now that's likely to end up with the same level of "really? That's what happens?" just because too much stagnation while trying to get the idea to take shape makes it less likely to. You have to push with what you can make work... I have to push with what I can make work so that it doesn't die entirely.
Imagine that kind of situation on a budget, a deadline, and whatever exchanges directors and producers throw into the mix. I seriously doubt I could do it. It's its own skill set.