Online violin lessons are worth it to learn from lots of different teachers worldwide, see various musical styles, and get better quicker to play for others. A professional teacher helps you learn the right techniques and get through any tough parts quicker.
However, an online teacher can't fix your arm, wrist, or finger position like they can in-person. The instructor must explain it all instead. Explaining how to tune the violin can be a bit tricky. For young children, parents should be present during the session to help the child stay focused.