I pointed out the other day how many good wrestlers entered the sport in the 1990s when it was young and much less established. Severn, Frye, Couture, Tito, Coleman, Kerr, Tom Erickson, Randleman and Hendo were all fighting by '96-97. All those guys would be HWs or LHWs today (well Hendo probably a MW. Come to think of it, Chael Sonnen's first MMA fight was 1997 thought he didn't fight again until 2002.
So even the mid-to-late 90s had a LOT more wrestling talent than we've seen in the last 5 years from MW to HW. I'm not saying they'd all dominate current MMA with their 1996 skillsets, but given modern training most of them would be beasts today.
As others have stated, there are plenty of good grapplers at WW and below and have been for some time.