PyTensor debug is of little use to PyMC users because users are not responsible for most of the graphs that PyMC builds under the hood for them.
You are absolutely correct to be puzzled (and even upset) by the default error message. It’s just that PyMC is a user of PyTensor and a very niche one at that.
That’s why we emphasize tools like model.debug or just doing pm.draw(var) to confirm whether shapes/values make sense as it’s often just shapes or bad parameter values, which shouldn’t require any deep understanding of PyTensor.