Err, I'm pretty sure there are some good quality developer builds in the last 10-15 years, maybe more so than the 20 years prior to that. 80s and 90s was pretty shit for new-build quality.
Definitely a sweeping generalisation on my part! I have looked round a fair few though, used to rent in one from around 2008 (Highbury stadium square) and now live in one from 2001. The former was meant to be more up market, but the latter is actually way better finished.
Hmmm - I wouldn't buy a new development / off plan house. As far as I can see, all modern developments of at least the last 10 years are garbage.