I always liked the oath, probably because I'm an RPer who likes little touches like that. To me its in the same vein as writing formal letters when conducting foreign affairs, having an invented calendar, etc. Yes it doesn't have much practical use but I don't think it's a serious impediment to gaining citizenship. If someone is really incapable of copy-pasting an oath and substituting their name in, I don't know if we could count on them to be particularly active anyway.
You make good points on whether or not the answers in the questionnaire should be necessary, and I think at this point it's been bandied around so much I'll just agree to disagree. As far as I can see it, the point of the questionnaire is so that if/when someone lies, we have hard evidence to punish them with if they later do something bad. If you're a spy and lie on the "other regions" part of the questionnaire, then get caught, we can prosecute you for lying or use your lying in a formal espionage trial.
To me, it's the same this as asking someone "Have you made any money illegally" on your tax return. No one is going to answer yes, but if you find out they did make money illegally, you can charge them with tax evasion.