You are right. Some aspects of GR are very difficult to understand by people who don't know the math behind it.
But, you see buzz me man, Gr does this one thing with all that high-falutin' talk it does. It makes testable and repeatable predictions, It says 'we are going to find this out in the universe' and you know, that is what we find later on. It says 'if we do this kind of experiment, we should get xxx kind of result', and we do.
Space might not be curved in the presence of matter like GR says, but by golly by gosh, things act as if it was. Now, I always said, if it looks like a duck , and it quacks like a duck, it's a duck.
Now, you see what makes them think space is curved? It is predictions about what will be found. It is testing of those predictions. Just cause you don't understand it. It is using a distant galaxy as a
'gravity lens'
You see, Buzz, as much as the eggheads like to figure out how to prove things they think are true match the predictions there is one thing they like even more. And that is to prove the 'standard model' wrong.