I agree with
@Ploshkin . Fabric scraps would work with something like a draft excluder or a door stop but for something as big as a pillow they woulf be very heavy and very hard because the fabric would compress with very little air left inside. Polyester fleece scraps would be better than cotton scraps
Think historical fillings - kapok and cotton waste compressed and became lumpy and hard, horsehair is coarse enough to spring back and retain some of the air but it's not soft, downy feathers were better but many people have allergic reations. Wool and fleece can be good but very warm and compresses over time. Metal springs were introduced to stop the collapsing - and then the synthetics came along; both foam and polyester fibres. They captured the market for a good reason.
Whilst natural fibres are nicer to wear and we all want to reduce our use of plastic there are times when it is the better option.