Either replace with good quality doors or paint …
Imho …. you got an offer above for cost on new doors or you can paint…
Painting is obviously cheap option …. replacement you add pelmets, architraves etc. But if you get quality ones they last and hinges don’t come out etc.
I used the cupboard door paint inside cupboards as I couldn’t remove the granite worktop and it’s really much better than I expected… but quality replacemet doors are much better than cheap ones… and some good hinges also make all the difference as well. A tin of paint goes a long way and you can touch up.later .. cheap doors are likely to be damaged or warp or screws come out and you have to use filler and dowels
If you have weird sizes I’d say either paint or get them made.