I would agree with you, but after a quick search of the laptop I see it was released in 2019. That's not really old enough for the battery to be this bad, unless it was overcharged way too often or something. No harm in checking, though.
Check the My ASUS software for an option to change your battery charging threshold. It should be at 95% or 96%, and if it is at 15%, change it. Here's a guide from ASUS on managing your battery health-
ASUS Battery Health Charging - Introduction | Official Support | ASUS Global
There are sometimes settings to set a charging threshold in order to preserve the battery capacity, like on a Surface that's on a dock all of the time.