every Trek series has That Season/Those Seasons; the growing pains seasons where the theme isn't quite set yet, the stories haven't kicked in, the characters haven't jelled.

TNG's first two seasons are horrible. Picard is a grumpy asshole, Wesley is a smug prick, Riker is a dick, nobody seems to like each other or remotely enjoy being there and so many of the episodes are godawful, preachy, alarming nonsense.
'The Outrageous Okona' and 'Samaritan Snare,' two of the lowest points in Trek history, are from this era.

but the fans stuck with it and the series really turned itself around during the 3rd season, which culminated with the by-now legendary Best Of Both Worlds - which was a high watermark for Star Trek and, imo, network television.

Deep Space Nine's first season was boring and sloggish but once the plot kicked in, it was allowed to transition into truly compelling television.

Voyager's Awkward Phase lasted four seasons. my wife cites the exact turning point as when whatserface, Neelix's wife, left the show and Seven Of Nine and her Ridiculous Breasts joined.
at that point, she says, everything comes into place and we are treated to some truly memorable television.
that I, personally, initially completely ignored because i just could not get through those first four seasons.

there were a lot of problems with writers. I personally do not think Brannon Braga was mature enough as a writer to lead Voyager; there are volumes to be said about the fucking abhorrent treatment of Garret Wang (his job on the show is to be humiliated, usually sexually) and the show... wastes fascinating concepts hand-over-fist.

for example, the Vidiians. the Vidiians are, conceptually, the most nightmarish alien concept in Trek history, they get one, maybe two really good episodes and then poof, nothing. they wibble out into irrelevance.

there's a lot more but it mainly boils down to "many of us (myself included) just were not willing to get through those first four seasons."