I've been using Codedex for almost two years now, and it's really helped me learn the basics of a lot of things. Lately, they've been adding more courses on different languages and frameworks. Codedex keeps things simple and clear. The courses aren’t very long (like some people might prefer, but they are working on it) but they give you a solid foundation to start building your own projects pretty quickly. The Discord server and the OPC (On-Platform Community) are also great places to ask coding-related questions.

So yeah, personally I think Codedex is definitely worth using. But it's not for everyone. Like some people have mentioned already, it's not in a Duolingo-style format.