> but I'm not very fond of the JS community nor the language itself. I've been wanting to get into C# for a while, but I'm not sure if the tooling and community is quite developed yet.

You got your answer, learn core

I'm not sure if asp.net core is production ready, I wouldn't use it right now for my projects and I also doubt ( someone correct me if this is wrong ) that established companies are looking for asp.net core devs, it might be quite hard to find freelancing jobs.

So it's probably a better idea to use node for freelancing.

Now combined, you actually don't like node, asp.net core is not production ready and companies are not using it (yet), what else could you do ? asp.net mvc, lots of jobs, solid mature framework and C#.

Edit: I also think that it won't be hard to switch from asp.net mvc to asp.net core.