Well, that's true. When they first came out, they were considered new school. But now I'd consider it a second wave of old school because if you compare 90's hip-hop/rap to now, you can see how much has changed.
Tragedy Khadafi
EPMD
Eric B. and Rakim
Das EFX
Marley Marl
Masta Ace
Pete Rock and CL Smooth
Gang Starr
Kool G Rap and DJ Polo
Geto Boys
All pretty much started within a year or two of my birth, so I consider it old school. Obviously some of them changed up the style to catch up with the times.