Yep, normally "bị" "được" express the mood of the teller, or if you are talking about someone, and use "bị" "được" will express your attitude towards the action, the events described in the conversation. For Example.. Cô ấy bị điểm kém môn Toán - She got a bad grade on the Math test =>she must feel sad because of that, and You think that is a sad news(in general, everyone thinks so ), so you use "bị". Cô ấy sẽ được đi dã ngoại với lớp vào tuần sau đó. - She will go on a picnic with her classmate next week!- => that's an exciting news, and everyone think so (in general ), so you use "được".

I think "bị" and "được" use to express your negative condition. In your examples, "I enjoy learning Vietnamese" means "Tôi thích học tiếng Anh" and "She had to go to doctor, although she doesn't enjoy it at all" means "Cô ấy phải đi bác sĩ mặc dù không thích lắm"

I think "Bị" is uesd to for meaning (tình huống xấu) and "được" is uesd to for meaning (điều tốt).

For me,i think that ''bị'' is used for negative meaning (bad things) and ''được'' is used for positive meaning (good things).