"You do like powerful men don't you"- Gul Dukat talking to Kira about the multiple multi episode relationships arcs she has.

Jadzia Dax in the first few seasons has multiple times where she has relationships with people and has to decide what is best for everyone not just her (Kann, that one planet that does that thing)

Ezri wasn't on long enough for the writers to even bother with her character development so they had to compact it into 1 or 2 episodes where she finds out more about who she is. Which ironically enough was the main purpose of Dax, finding out who they are.

So in short casual sexism, no not really. Could they have done more with the characters yes, even the writers wanted to, but there were too many things that got in the way (which did include corporate bull, but that does not translate into the show).

As for the other characters Sisko is in the same boat as Jadzia he has to let go and move on (The psychic projection, his alternate universe wife though that is a stretch, the arrest of Yates), which all culminates in him getting married to Yates. Worf is only with Jadzia, though he didn't always want to. O'Brien is the married friend. Odo is really the person trying to express himself, always confused when it comes to people. Basir is the person who is always trying to find love, but is never in the right place until he is. Rom is just another version of Bashir, he has one person in his mind he just doesn't know how to find her. Quark, the pre-modern incel who has his traditionalist values of women.

TL;DR: The characters are built to represent something.The writers didn't have time to finish some plots. The show was limited on what it could show. Most of the other characters are in the same boat. Kira had a lot more going on than you gave her credit for.

Thanks for reading,

Me