>>1200Using C# .NET for an image board project is like using a bazooka to crack a peanut, still if it's just for learning you aren't wasting your time at all. You will learn a lot. It will make you a good programming sophomore. You will stand out from the React/JS bambinos by a decent amount.
When you have finished your project you can make a similar project in, say, a Python or PHP based framework and you will truly appreciate the benefits these weak soy languages can bring.