Are online courses a good idea to improve skills?
Yes. I have completed some online courses in the recent past and found them a useful way to improve my skills.
It doesn't matter whether you learn online or offline. It's a matter of your motivation only. If you have a goal and if you are ready to do anything to achieve it, you'll succeed. For example, I'm currently learning Spanish with an online teacher because I work for a Spanish company and need to communicate with native speakers of Spanish almost every day. I have no time to go to a teacher, this is why I've decided to try to learn Spanish online. I've compared several popular services including https://www.tutoreye.com, https://www.revolutionprep.com and https://eurekly.com and finally chose the latter (reasonable prices, delightful reviews and so on). It's my first experience in e-learning and it turned out to be just as effective as learning in a traditional way. No matter if you hire a personal tutor or take a course, if you are motivated enough, it will help you improve your knowledge. Which course are you considering BTW?