.NET Core is a nice step from Microsoft, but even 2.1 still only supports a fraction of .NET enterprise software, let alone Java comparable software solutions and host platforms.
We're roughly what 3 years in? It's to be expected, but what it does currently support is fairly impressive. Having used ASP .NET Core on a couple of projects I would say it covers enough for web development, right after Python I'd much rather do web development in C# as a result.
I do agree though it isn't a completed product yet, but what's already there is fairly capable depending on what you're working on.