misconceive

To misunderstand.

1694, William Congreve, The Double-Dealer Nay, misconceive me not, madam, when I say I have had a gen'rous and a faithful passion, which you had never favoured, but through revenge and policy.

To judge or plan badly, typically on the basis of faulty misunderstanding.

HS2 has never had that. It was missold, misnamed and misconceived. It was promoted as a piece of engineering, rather than as a vital part of the railway.