They are completely function
Try peel and stick wall paper or hang curtains in front of them
You could add moldings to them.
Maybe replace them with a different type of door? Barn doors are great. Or paint them?
Bi fold or sliding doors? If they are sliding just paint them and you could add decals for some unique and eye catching decor ideas.
Definitely some paint! I love the look of dark gray doors right now! But white would also update them and make them look fresh. I would use a paint specifically for doors and trim and use a really good bonding primer before the paint.
You can use thin pieces of wood and add them to look like they are higher end doors. Shaker style, farm style etc.