I don't understand.

It looks to me as if Adams's whole point is that marriage isn't supposed to be primarily an economic arrangement, it's supposed to be an institution that provides couples with a stable context for loving one another, raising children, etc., but in fact (so he says) the only way in which it works well is economically, and in any other respect it's a failure.

It's as if I wrote "Smith's new book makes a very good doorstop, but in all other respects I have to say it seems to me an abject failure". Would you say it speaks volumes that I view Smith's book as a doorstop? Surely my criticism only makes sense because I think a book is meant to be other things besides a doorstop.