Likes and dislikes

좋아하다 is built from 좋다 'to be good' plus -아하다, an ending that turns a feeling into something a person does. Once liking is an action, the person who likes is the subject and the thing liked is the object, exactly like 커피를 마셔요, so it takes 을/를. That is also why 좋아해요 is the form to use about other people: 친구는 커피를 좋아해요 'my friend likes coffee', with 친구 'friend', reports what they visibly do. It is the same idea you met on day 22, where another person's wants needed a different form.

좋다 is a describing verb, 'to be good', and a describing verb has a subject but no object, just as 매워요 on day 12 describes the food. So the thing takes 이/가 and there is nowhere for 을/를 to go. 좋아요 reports your own reaction, which is why it suits the moment: tasting something, seeing a view, agreeing to a plan (좋아요 on its own means 'sounds good'). Mixing the two, 커피를 좋아요, is the classic mistake: the particle has to match the kind of verb.

Korean speakers soften dislikes by negating the positive rather than stating the negative. 별로 안 좋아해요 'I am not especially keen' leaves room for the other person, while 싫어해요 closes the door. The pairs mirror each other exactly: 좋아해요 and 싫어해요 take 을/를, 좋아요 and 싫어요 take 이/가. If you learn each verb together with its particle, as one chunk, you will not have to stop and think about it.