Having used this framework you absolutely use it to train and create novel classification models. I used it to train financial transaction classification models, it works quite well.
You can absolutely train your own models. Your comment is patently false and a fraction of the time it took to write it should have been spent reading that API you have so inaptly described. I encourage you to delete it.
You can use it to train the models that they have built. You can't make new models. I've done quite a bit of research into ML.NET because the nomenclature lead me to believe that it can fill the role of Tensorflow.
ML.NET only has what's in the box, it's turn-key. You guys have an explicit ResNet18 assembly, as one example. While this is incredibly useful, it is not appropriate to call such a library a framework.
A possible improvement would be:
ML.NET is a machine learning API which is aimed at providing turn-key models for infusing ML...
If you wanted it to classify as a framework, you'd have to provide something like Tensorflow does: a way to develop new and novel models.
That's just my opinion, but a few people seem to agree.