Quite agreed; but he was contemporaneous and there is some evidence that the founders read his commentaries on English law.
Without those, with respect to legality and constitutionality, you have nothing but your opinion and the opinion of Blackstone.
Except you miss one salient point: the Constitution was not written to be translated by lawyers and handed down to the people, but it was written in generally plainly understandable language so that every man might know what the government could and could not do. IOW, the opinion of myself [and every other American] is relevant. — As an example, if one could convince a large majority of the people that in all cases searches w/o warrants were unreasonable then the legal system would change [for the better, IMO] because of the 4th Amendment's requirements.