it isn't my, his, etc. thing

not (really) (one's) thing

Not something one particularly enjoys or is good at. A: "Do you want to come with me to the concert this Saturday?" B: "No thanks, heavy metal isn't my thing." I'll give it a try, but car repair isn't really my thing.
See also: not, thing

it isn’t my, his, etc. ˈthing

it is not something that you really enjoy or are interested in: I’m afraid pubs and clubs aren’t really my thing. I’d prefer to go to a restaurant with a few friends.
See also: thing