In the theoretical sense, I agree with that, but in a world of social interconnections, we need a meaningful framework and vocabulary for judging these sorts of things. While I believe that true objectivity is hard (and maybe impossible), I think there's a lot of social value in coming up with widely accepted definitions of rational vs. irrational, at least on a case-by-case basis.

It has meaning. It means "we have insufficient information" or "something is going on here that we don't know about or understand."

In any case, that's a false dichotomy. Governments are not uniform entities, and there's no point talking about them as if they are. Governments, like people, do some rational and some irrational things.