Of course they are, however before picking up any course (no mater if paid or free), make a research, check comments and be sure it will help you grow!
During the pandemic, I took loads of free courses alongside some very affordable Udemy & Coursera courses. These experiences essentially led to my career pivot!
I also love that LinkedIn allows you to feature most courses on your profile as well.
I mostly take the courses for self-improvement and often just watch the video lectures and few quizzes based on that. That's something worthy, in my opinion.
it depends if you aim is to get knowledge or to get a certificate, if its knowledge, you can try edx, there are many courses that will give you access to video for a limited time, so you can gain the knowledge, but you won't get a certificate, I still found it very helpful.
Free online courses cover some of today’s hottest subjects, from artificial intelligence and machine learning to social media marketing and search engine optimization (SEO). If you’re unsure about using new skills professionally, a free online course is a great way to dip your toe in the water.
It depends on the value that we give to them.
If we are really motivated to learn from free materials, I'm sure we'll gather a lot of knowledge.
sometimes, even from premium courses, we might not learn much.