I think it's a fair point but only to some extent. We've seen time and time again that if you put out a hyper-detailed position paper your opponents will simply rip it to shreds, which distracts from the overall vision.
I want my think tanks telling me how to best soak the rich. It's enough for my presidential candidate to announce he favors soaking the rich, as distinct from the rest of the field who differ only in the degree to which they'll pucker up before fellating them. There is plenty of time for details after election, and of course those details will change a dozen times during the sausage-making process, so holding yourself to your campaign announced details is suicidal.
So I agree with you to the extent that, say, a candidate should say he favors replacing Obamacare with a single payer system. But as to the gory details of that system, that's something that will be fought over in the Oval Office and the cloak room, and there's no point in boxing yourself in before you get started.