They still hold up today, as evidencex by occassional reprints and ongoing audiobooks of them. If they didn't still have enough quality to them they wouldn't be commercially viable. No other tie-in series stays in print. Even Star Trek doesn't get reprints any more.
There is more than just nostalgia in play for DW Target books!
Oh that's a pity. I was looking forward to those, particularly the Dalek ones. I was updating my Target list only the other day to put them on. I was pondering whether I need the target version of City of Death as well as the original hardback.
Yes, I know it's abridged, but not having the Target one leaves a gap in the collection the hardback doesn't really fill. That's a heck of a delay, Corona related or not. Eight months from the original date!