For some reason, you fail to understand my point. A pragmatic approach means the Union would have existed,
with slavery, for quite some time. You said, Lincoln wouldn't have felt the Union was worth defending if it allowed slavery. It would have existed, with slavery, under his approach. Maybe I can explain it this way.
Pragmatic approach = slavery exists for some time.
Slavery exists for some time
≠ he wouldn't have felt the union was worth preserving
To the other point. It's not surprising that the Southerners didn't grasp the economic changes. Plenty of people haven't recognized economic/technological changes at a given time. For example, in the 80s, the phone companies didn't realize how cell phones would change their business. The ignored the technology. Now, these are intelligent, educated people, who are experts in the field of communications, and they couldn't see what was coming. It's no surprise that a mostly rural population in the 19th century would be slow on the take.