One truly remarkable building in downtown Seoul is the Seosomun Apartments near the Seoul Police Station which have somehow managed to survive in their original form to the present day. The building represents well the simple structures that went up across Seoul in the 1970s, especially under Mayor Kim Hyun-ok. 
I actually have a weird fondness for these buildings. I think some of them should be kept.
The problem is that they were awful when constructed, age horribly, are badly designed and were built on the super cheap. They have, in fact, few redeeming features except history.
I find that a shame. I see the justification for getting rid of them all. But I think it’s sad that none would be left to mark that period of Seoul’s history. But preserving and possibly re-purposing them: How could this reasonably be done? They’re awful.
That’s a serious quandary that needs to be addressed. It’s not unique to Seoul, but the scale of this problem is immense in this city.