Honestly, I think the biggest problem is that Colm Meaney and Rosalind Chao have negative chemistry. They probably cast her in TNG thinking that O'Brien was a second-tier supporting character, and that she had good "nervous bride" energy for her first appearance in "Data's Day," and that would probably be about it for the character. It's not the actor's fault that a fictional pairing that wasn't very well thought-out on the writers' and casting director's part didn't turn out to be strong enough to survive as a primary plot driver.

That said... I would have loved to see Miles and Keiko go through an amicable divorce. They virtually did, between Keiko basically throwing Miles and Kira together during their pregnancy and Keiko's long-term journeys to Bajor. It wouldn't have been that much further to just have them realize that they'd grown apart and agree to separate, and it could be a way for Star Trek to explore a subject that a lot of people had real-life experience with. I don't suppose that mid- to late-90s Star Trek producers would have gone for it, but there was some real narrative potential there.

While it's fun to poke at Keiko, I think Winn Adami is a worse villain.
Also: Gul Dukat is the best antagonist in Trek.

The problem with Keiko is that she just isn't on miles level so she comes off as self absorbed in the face of a genuine man who is literally out there saving the alpha and delta quadrant weekly.

She's tolerable in TNG because she's more of a plot device for Miles but for DS9 they lean into the fact that she's a mother and a wife and I guess the point of her character was to show the dynamics of family life for non-officers for star fleet. there's no way Keiko should know whats going on - it's way over her head - she's just trying to live a normal life, but she has absolutely no deference for the fact that she's married to one of the most hard working and honourable people in the whole galaxy and that really just makes her a nag and annoying af.

Jokes on you, O’Brien is CLEARLY into punishment.

The food-based psychological torture she puts Miles through is entertaining at least

Only at early season 2 of my forgot-everything rewatch of ds9. She can’t be that bad, can she?

All I remember from Keiko in DS9 is she preparing algae while Miles pined for some mutton and potatoes. Perhaps a rewatch is in order.

Yes. And her (the actresses) role in Three Body Problem is like that characters development. If you want some Keiko head cannon, bc.. while some femme baddies were written really well (like Win, probably only Win) there's a hesitation, a lack of commitment to the thought project of darkness in a loving mother, doting wife.