not quite the thing
Not considered socially acceptable, respectable, or appropriate. Primarily heard in UK. She found herself pregnant without being married, which was not quite the thing for a lady in Victorian England. Surely you knew that wearing a tracksuit to a job interview wasn't quite the thing, right?
not ˌquite the ˈthing
1 not considered socially acceptable: It wouldn’t be quite the thing to turn up in jeans and trainers.
2 (old-fashioned) not healthy or normal