Down jackets are lightweight, soft, and highly insulating. A jacket made with nylon outer fabric and filled with down weighs between 500 and 1000 grams, which is 1/6 to 1/2 the weight of other winter clothing. Because down is soft, it is comfortable to wear as filling. Down is less prone to fiber clumping; the outer fabric is often made of high-density coated fabric, which helps retain more air inside the garment, resulting in excellent insulation.
Down jackets generally use more than 90% white goose down or more than 90% white duck down. A true down jacket with more than 90% down has strong insulation, high loft, and is lightweight and comfortable to wear. Down jackets with a down content of 90% and a fill weight of 230g to 320g (depending on the size) are generally suitable for environments with temperatures around -20°C to -30°C in northern regions. If you touch a down jacket and feel a lot of feather shafts, it's definitely not 90% down. If you press down on a down jacket and then release it, 90% down will quickly fluff up and return to its original state. If you press down on it and then release it, the down jacket is still flat. It's possible that the down jacket you bought doesn't have 90% down, the fill power is insufficient, and its warmth retention is very low.