Michelle Williams has talked about how she struggled at the time with her character not really being a fan favorite.
In the early years, there was way more hype about Katie Holmes as the next big thing and as the pretty one, compared to Michelle. By 2004, much of that may have subsided in the media but that doesn't necessarily change how Michelle felt about herself. I don't remember her making any best dressed lists before the awards season for Brokeback Mountain. I understand how she wouldn't have viewed herself as the glamorous type circa 2004, compared to her peers.
I watch Dancing with the Stars and often some of the claims to fame are dubious but often IMO the viewers with the, "I've never heard of them," complaints have clearly checked out of noticing pop culture sometime in the 1980s, and I guess expect the broader world to cater to their limited tastes and essentially stop turning with them. I always want to say, "Just because you stopped paying attention, doesn't mean that things stopped happening."
Michelle Williams has mostly stuck to independent movies in the last decade and has been nominated for three Oscars, a Tony and won a Golden Globe since 2008. She got unwittingly embroiled in an equal pay controversy when she made All the Money in the World and has appeared in more mainstream studio films in the last two years, The Greatest Showman, I Feel Pretty and Venom. She's starring as Gwen Verdon in the limited series Fosse/Verdon that began airing earlier this month.
I could have done this post with links to Michelle Williams' pages on IMDb and Wikipedia, but it's so easy these days to look things up for yourself if you really want to learn more. I suppose it's even easier for people to throw out some variation of, "I don't know her," and actually think that's a relevant, worthwhile or clever line of attack on a celebrity. When, really, they are saying so much about themselves, none of it being particularly flattering.