It's a bit harsh to say that a club like the Roosters or Souths have 'kept their traditional' design, yet someone like the Bulldogs hasn't. Really outside of the shocker 2018 kit (which was still easy enough to recognise) the Dogs have had a design which arguably is as close as you are going to get to their 73 - 96 designs..
Bulldogs 2019 Kit:
Bulldogs 1990's:
Bulldogs 1980's:
Sure some design elements have changed, ie. the V is a consistent width, versus in the mid-90's especially it seem get thinner the closer it go to the point, and the bar on the sleeve is now wider, but there were times when the Roosters kit didn't have red bars on the sleeves, and Souths only had 3 red horizontal bars, not 5 as they do now.
Regardless all 3 clubs have kits now which when wearing their home at least, fans from most eras would recognise immediately and consider relatively unchanged.
With the Sharks rumoured to be going back to their block design, the Eels making their home 1986 inspired, Warriors & Cowboys basing theirs off 1995, Knights off their 1988 design, Penrith from 1991, and well Dragons always have a V for home, hopefully most clubs are moving to a more consistent template for their home kit. Canberra as well whilst the tri-colour lines have moved up and down the sleeves a few times in recent years, the core kit has stayed the same.
Considering clubs can bring out between 5 - 7 kits a year, it's possibly not unrealistic for the NRL to consider getting all clubs to have some core 'template' which has to always be their 'primary' and only permit minor variations year on year (which will happen with jersey cuts, sponsorship placements, etc).
Caters for both the more traditionalist / brand focused and for experimentation. For some clubs, like the Roosters, they've made it clear that the experimentation doesn't appeal to them, but for those with no identity (Titans anyone?), it might save them a bit from themselves.
