In fact, you are assuming something that is not the case.
The descriptions given are not wanton assumptions made by "Mainstream" scientists at all. But it is also true that there are no direct observations up close and personal.
But from far away, we have made observations including this one.
While the word singularity often is used as synonymous with black hole, the black hole is effectively treated as a singularity in the mathematical formulas. There may well be a difference. Without better observation of black holes, we are unable to take measurements that can increase the accuracy of predictive theory.
There is one thing, however, which you are very much in error of... an assumption so large that I am quite curious how you reached it: You claimed that light can escape from a black hole. What makes you think so?