I think the real problem is describing 'singer songwriter' as a genre.

Being able to sing well is a great talent, so is being able to write good songs. If someone is able to do both then they are doubly talented. Sometimes singers are put under pressure to perform 'original songs' meaning ones they have written themselves. They may not be particularly good writers. Similarly songwriters may be tempted to record their own material, even if they are not good performers.

People who profess not to like singer songwriters would rule out listening to a lot of very talented individuals, but as others have indicated they normally exclude the ones they like from the genre.

As to whether or not the output of some/all singer-songwriters is folk music - I'm not going to go there thanks.