As far as I'm concerned, building a good repertoire includes the requirement to consciously add variety, so that any set will have variations of pace, sentiment and modality, with a sprinkling of chorus songs.
Singers I have known have constructed their song lists under different headings, hoping that simplifies the putting together of a programme. I use three basic categories - narrative (including ballads), lyrical and comic; but I know other singers who organise their lists according to pace, and I well remember that Ray Fisher had a category that she called 'dowie' ( a Scottish word meaning sad).
When I'm in the audience at a concert or in a club, I know how much I appreciate some variety in a set, so I would strongly urge any less experienced performers to work on a good range of material, even if it initially feels as if it's outwith their comfort zone -- it all comes good in time!