Kant was a philosopher. And, IMO (which I have stated before), philosophers take a lot of time to get to what they see as truths.
Other philosophers try and shoot them down.

Quite so: and that is exactly analogous to 'peer review' in science. You present your view, others criticise it and then third parties get to choose which is the most convincing. That is one of the reasons that philosophy and science are not simply 'belief systems'; the reasons why you to propose your view must be open to a full and detailed examination of the reasons you believe it and while you are free to continue to believe whatever you like, what you as the proponent end up believing is not the point of the process.