I'm actually a big fan of the Categorical Imperative. In the least, I find it morally illuminating, if not definitive, because it gets people to think about the moral principles behind their actions and avoid contradiction in their moral views, particularly hypocritical or self-serving contradiction. I suspect that any rational ethics (whatever that is) would have Categorical Imperative-like thinking involved.

I don't think that the Categorical Imperative, at least the way I understand it, requires radical honesty.

If I lie to the Nazis, I "make it my maxim" that it is justified to lie to authorities to save an innocent person from death (when I can provide a reasonable argument that the person is in fact innocent and the authorities are wrong to try to kill them). Can I, at the "same time", "will" that this maxim "become a universal law" without engaging in "contradiction"? Yes, I can.

My maxim is not that I think I have the right to decide, in general, who deserves to know the truth and who doesn't. Rather, my maxim that is that potential murderers of innocent people don't deserve to know the truth, when I can provide reasonable argument that they are truly innocent and that giving them up would lead to unjust harm to them.

Now, say that WWII is over, and Hitler himself is hiding out in Germany with his sympathizers, when Allied soldiers come knocking. Would the family hiding him be justified in lying, according to my maxim above? If they were justified according to my maxim, while I maintain that they would be unjustified in protecting Hitler, then I would engage in contradiction if I acted according to that maxim. Yet I hold that Hitler's benefactors are not justified by my maxim, because they cannot provide any reasonable argument showing that Hitler is innocent and that he does not deserve to be captured.

The problem isn't Kant's Categorical Imperative, the problem is that he was sometimes incorrect about what it implies.

P.S. I agree with your main point of avoiding straw men in discussions simply because they were advanced by famous, but discredited, philosophical arguments, unless the author thinks that there is something particularly illuminating about doing so.