This is fantasy. There are plenty of big hits, just no more head hunting. Guys like NAK get suspended for throwing elbows.
What benefited smaller players wasn't eliminating fighting, but cutting down on grabbing, hooking, slashing and interference.
That let them skate unimpeded (or at least with less contact than before).
In response the league has gotten faster (and slightly lighter, by about 5 lbs), which means the windows are smaller, forecheckers are faster so D-men have less time and have to win board battles to maintain possession. Checking lines have fewer 220 lb forwards, but more 200 lb players with above average speed.
In the future, as overall speed increases, skilled smurfs will have less of a competitive advantage as bigger players can still check them and lean on them, but there will be less room to skate. Bigger players also have a wider stick radius to break up plays with the speed to get to spots where they can block and harass smurfs.
Eventually, like all evolutionary battles, the league will come to a new equilibrium.