It may be that denim as a fabric is suitable for some garments. Jeans however are intended to accentuate that which should be concealed. Leggings are even worse. God explains that the correct response is shame, not showing it off.
I Timothy 2:8-11 I will therefore that men pray every where, lifting up holy hands, without wrath and doubting. In like manner also, that women adorn themselves in modest apparel, with shamefacedness and sobriety; not with broided hair, or gold, or pearls, or costly array; but with good works. Let the woman learn in silence with all subjection.