well, step one would be to paint them white. or get new ones that are more in style, even have them made.

The closest in the bedroom look like they could be changed to sliding doors or two standard doors. you could mount mirrors to them and box them in as well.

I might consider removing the ones in the master bath, it having open shelving with baskets etc.

do you hate how they look or hate how they work? how about painting them, and their trim, the same color as the wall?

We had folding doors on our laundry room and I hated them.....always getting in the way of our basement door....took them off and like the look. In our bedrooms, we have sliding doors and it looks like you could have that also. Be sure when you install the doors, that they run smoothly on the track and are the right height for the track so they don't fall off when you open and close them.

Google “bifold door conversions”...
Options include sliding doors/bypass doors, French doors, barn doors...

i just painted the bi-folds in my laundry room. I did 2 rounds of spray paint to get those hard to reach spaces, then went over everything with a brush. It was cheap & took less than 2 hours. I'd probably splurge on new doors for "more important" rooms, but painting was quick, easy & I'm pretty much the only one who seems them anyway :-)

Thanks for the suggestions so far! I don’t like how they look, but really hate how the work. They have always just felt cheap and kind of janky to me. I really like the idea of removing the door from the bathroom closet and converting the others to French doors. Has anyone had success doing that as a DIY?

I don't think it would be very difficult, after the first conversion the rest will be easy, it will be more expensive than simply painting the bi folds, by a lot and the new ones will have to be finished as well. Pick your poison.

When we moved into this house, the first thing I did was replace sliding doors on closets with bifolds. In the last house, the biforls were like yours, and I painted them white, Massive improvement. If the doors are flimsy, you can buy heavier ones. But I'd never go back to sliding doors with the terrible access.

I'd do french doors instead. Maybe with a magnet close. Won't be cheap to do but, in my opinion, a huge boost in appearance and functionality. I share your thoughts about bi-fold doors.

There are different qualities of bifold doors so you might want to go to a good door store and see how they felt.

I have a combination of closet door styles in my home. Sliding doors (IMO) work best with relatively wide closets and even then I am sometimes frustrated a bit when I need to slide back and forth. In my bedroom I also like that they function as really good full length mirrors - as well as providing a mirror image of my views.

Bifolds work well because I have complete visibility and access to the entire closet and obviously the function where a swinging door would impede egress.

We are currently in the middle of this project transforming a set of bifold doors into these French doors. It has been very simple so far (almost ready to paint) and we've already gained accessible closet space on the sides that the bifold doors previously blocked.

https://www.brightgreendoor.com/french-closet-doors/