It's always hard to compare shows from different eras. Perhaps DSN pushed it as far as it thought it could get away with. Fast forward a decade later and because previous shows pushed the boundry a new show tries to push the boundry a little more.
I can see that. I also think its because its Star Trek. Because Star Wars and Gundam came out in the 70's and both were able to do war much more dramatically. In some ways I fear that the issue was that the writers were too TNG which was a peaceful non-violent exploration show. Writing for war was out of their area. One sees the same issues when they attempted to do the Ent world, which was supposed to be gritter too.