Should I do a course on Design, online?

Short answer

The map is not the territory.

Long answer

Design needs a more inclusive learning environment. Skills, yes, you can pick up online. There are people who have learned entirely from online content and gone on to do serious work. But the very act of design needs some level of criticism, some level of feedback, which online may not make easy.

When you enroll in a design school, you are not just learning skills. You are learning from peers, from a mentor, from the diversity you are exposed to. Much learning happens through discussion, through a community of co-learners.

The real question before any course is your intention. Is it a certificate to land a job? Is it to find the right mentor? Is it early learning or a deeper dive? And there is the money factor. If you are taking a loan to study, that changes everything. Define what you want, then choose.