Having learned the basics of OpenGL in a 10 week university course that was primarily focused on modeling statistical data, I would definitely think OpenGL would be a reasonable option for an easy to learn graphics package for 2D real time modeling.
Although there’s certainly complexity available to OpenGL you don’t need to wrap your head around all these features you don’t need, to make a basic project with a graphics screen is almost all boilerplate code that you don’t need to understand well, you could practically copy and paste from a sample project. For example, here are some sample programs that go with a textbook on OpenGL. Configuring the whole library to be part of your project is just a matter of adding a couple .lib files to a certain spot in the configuration settings, it doesn’t take a lot to make it “do something” and then you will only need to familiarize yourself with a small subset of the features, to me it almost seemed easier than, say, drawing 2D stuff in Java.
I don’t really know any of those other modeling tools well, just thought I’d throw out there that I wouldn’t write that one off too quickly as being “too complex”, it’d be reasonable to consider, even without a huge background in C++ or graphics, etc.