Maybe it's just me, but I think I'm actually seeing MORE diversity in OLs recently. Perhaps enough people are tired of the cookie teams to try something else? The OBP strategy is good one, but for a long time the dominant strategy was deadball pitchers, low-IP starters in the pen, and an offense largely comprising low-BB singles hitters with speed, in Astrodome or Dodger Stadium.
Right now I'm in a couple of OLs and there is a nice variety of strategies being employed by the best teams. I'm about to face off in the LCS against a Mize-Ruth-Cy Williams team that hit 236 HR in AFCS. Coors teams are making a comeback. There's a division leader in another league with an A++++ range team in Hilltop (haven't seen one of those in a long time.)
There's still plenty of the Joss-Coleman-Castillo-Dilone-Raines teams (and to be fair, I use some of those guys too), but I think enough owners are seeing that there are other ways to win.