I have a similar problem with my
left thumb! Ever since I started using TouchID (when the iphone 6 came out) it just refused to work with my left thumb, but works very well with my right thumb. My left thumb has more creases in it, but it's not like it's disfigured or anything. Just a normal 40-something year old thumb
I re-scanned my left thumb many times. It would successfully scan, and work immediately afterward. Then it would stop working most of the time. My iPad Pro seems to like my left thumb a little bit more, but it still doesn't work as well as my right thumb does. I guess that's why I like FaceID more. Of course FaceID works with gloves on, and you can train it to recognize you with and without glasses, shaven or not, etc. And yes, TouchID can have a problem with dirty or wet fingers and thumbs. Definitely won't work with gloves, so Winter is a good time to have FaceID.